U.S. patent number RE29,285 [Application Number 05/694,047] was granted by the patent office on 1977-06-28 for method for concomitant particulate diamond deposition in electroless plating, and the product thereof.
This patent grant is currently assigned to E. I. Du Pont de Nemours and Company. Invention is credited to Theodore Peter Christini, Albert Lawrence Eustice, Arthur Hughes Graham.
United States Patent |
RE29,285 |
Christini , et al. |
June 28, 1977 |
**Please see images for:
( Certificate of Correction ) ( Reexamination Certificate
) ** |
Method for concomitant particulate diamond deposition in
electroless plating, and the product thereof
Abstract
This invention is a method for depositing on an article a
coating containing at least one member of the group metals and
metal alloys plus particulate dispersed diamond comprising
contacting the surface of the article with a stable electroless
plating bath consisting essentially of an aqueous solution of
soluble constituents of the group, electroless reducing agent
therefor, a suspension of diamond particles therein and a
stabilizer, and maintaining the diamond particles in suspension
throughout the bath during the coating of the article for a time
sufficient to produce a preselected depth of coating on the
article, and the coated article per se.
Inventors: |
Christini; Theodore Peter
(Dushore, PA), Eustice; Albert Lawrence (Lewiston, NY),
Graham; Arthur Hughes (Wilmington, DE) |
Assignee: |
E. I. Du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
26992553 |
Appl.
No.: |
05/694,047 |
Filed: |
June 7, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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208233 |
Dec 15, 1971 |
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Reissue of: |
341529 |
Mar 15, 1973 |
03936577 |
Feb 3, 1976 |
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Current U.S.
Class: |
428/426; 51/309;
106/1.12; 427/438; 428/433; 427/305; 428/323 |
Current CPC
Class: |
C23C
18/1662 (20130101); C23C 18/38 (20130101); D02J
1/08 (20130101); C23C 18/32 (20130101); Y10T
428/25 (20150115) |
Current International
Class: |
D02J
1/08 (20060101); D02J 1/08 (20060101); D02J
1/00 (20060101); D02J 1/00 (20060101); C23C
18/16 (20060101); C23C 18/16 (20060101); B32B
015/00 (); B05D 003/10 () |
Field of
Search: |
;428/426,323,433
;427/438,305 ;51/309 ;75/.5R ;106/1 ;29/195,196.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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709,470 |
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Jan 1968 |
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BE |
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1,621,206 |
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Jun 1971 |
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DT |
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Other References
Translation of German Offen. 1621206..
|
Primary Examiner: Welsh; John D.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuous-in-part of U.S. application Ser.
No. 208,233, now abandoned, filed on Dec. 15, 1971.
Claims
What is claimed is:
1. A coated article formed by electroless plating comprising a
co-deposited uniform dispersion of diamond particles secured by
substantial nucleation within a metallic matrix comprising one of
the group consisting of: (1) an alloy including a metal of the
sub-group made up of nickel, cobalt and mixtures thereof with one
of the elements phosphorus, boron and mixtures thereof and (2)
elemental copper, deposited on a supporting substrate consisting of
polymer, metal, ceramic or glass.
2. A method of forming a composite structure on an article by
electroless plating comprising immersing said article in a stable
electroless plating bath having a composition effecting concurrent
deposition of particulate diamond .Iadd.having a particle size in
the range of 0.1.mu. to 75.mu. .Iaddend.dispersed in a metallic
matrix comprising one of the group consisting of: (1) an alloy
including a metal of the sub-group made up of nickel, cobalt and
mixtures thereof with one of the elements phosphorus, boron and
mixtures thereof and (2) elemental elemental copper, while
maintaining agitation of said bath retaining said particulate
diamond in suspension, and removing said article carrying said
composite structure from said bath .[.when.]. .Iadd.after
.Iaddend.said composite structure has been plated out on said
article in preselected amount.
3. A coated article formed by electroless plating consisting of a
shaped substrate, a metallic matrix coating deposited on said
shaped substrate, and a uniform dispersion of co-deposited diamond
particles secured by nucleation bonding within said metallic
matrix, wherein
1. said substrate is one of the group consisting of (a) an organic
polymer, including reinforced organic polymers, (b) metals, (c)
ceramics, (d) glass,
2. said metallic matrix consists primarily of at least one of the
group consisting of (a) nickel, (b) cobalt, (c) copper, together
with smaller proportions of other components commonly codeposited
from electroless plating baths, and
3. said diamond particles constitute from 1 to 50% by volume of
said metallic matrix, with a particle size ranging from about
0.1.mu. to about 75.mu., but predominantly in the size range
between 0.5.mu. to 25.mu..
4. A coated article formed by electroless plating consisting of a
shaped substrate, a metallic matrix coating deposited on said
shaped substrate, and a uniform dispersion of co-deposited diamond
particles secured by nucleation bonding within said metallic
matrix, wherein
1. said substrate is one of the group consisting of (a) an organic
polymer, including reinforced organic polymers, (b) metals, (c)
ceramics, (d) glass,
2. said metallic matrix consists primarily of at least one of the
group consisting of (a) nickel, (b) cobalt, (c) copper, together
with smaller proportions of other components commonly codeposited
from electroless plating baths, and
3. said diamond particles constitute from 1 to 50% by volume of
said metallic matrix, with a particle size ranging from about
0.1.mu. to 75.mu. but predominantly in the size range between
0.5.mu. to 25.mu., and said diamond particles individually consist
of many individual crystallities tightly bonded to one another in
essentially unoriented pattern giving polycrystalline particles
having many irregular projections, ledges and craters.
5. A coated article formed by electroless plating according to
claim 3 wherein said article is a fluid jet provided with a
discharge orifice.
6. A coated article formed by electroless plating according to
claim 4 wherein said article is a fluid jet provided with a
discharge orifice.
Description
BRIEF SUMMARY OF THE INVENTION
Generally, this invention consists of a method for depositing on an
article a coating containing at least one member of the group
metals and metal alloys and incorporating therein particulate
dispersed diamond comprising contacting the surface of the article
with a stable electroless plating bath consisting essentially of:
(1) an aqueous solution of soluble constituents of the group, (2)
electroless reducing agent therefor, (3) a suspension of diamond
particles in concentration in the range maintaining fluidity of the
bath, (4) a stabilizer for the bath of concentration in the range
from that sufficient to prevent decomposition of the bath upon
addition of diamond particles thereto to that retaining plating
capability of the bath, and (5) additives facilitating electroless
plating per se, and maintaining the diamond particles in suspension
throughout the bath during coating of the article for a time
sufficient to produce a preselected depth of coating on the
article, together with the product of the method.
DRAWINGS
The following drawings, some of which are reproductions of
marked-up photomicrographs and some of which are partially
schematic line drawings, depict the composite structures obtained,
the wear tracks developed during running yarn frictional testing of
the several types of structures, and the test apparatus and its
component orientation with respect to test specimens, plus a
preferred deposition apparatus, in which:
FIG. I is a typical photographic plan view (6340X) of an
electroless Ni-B alloy/12.mu. synthetic diamond "A" composite with
the several most important structural features indicated by
characteristic numerals,
FIG. II is a typical photographic plan view (6480X) of an
electroless Ni-B alloy/9.mu. natural diamond composite, with
individual structural features identified,
FIGS. III(A)-(E), inclusive, are partially schematic
representations of the Accelerated Wear Test apparatus employed,
and the results obtained, in the evaluation of the best composite
coatings laid down by this invention, as to which (A) is a plan
view of the test apparatus (B) is an inset perspective of the
running yarn course over the surface of a specimen in test, (C) is
a side elevation view, partly in section, taken on line IIIC--IIIC,
FIG. IIIA, (D) is a perspective view of the relationship of running
yarn line to specimen in an invalid Standard Test which yields
corner notching [FIG. IIIE(M)] without a wear track on the
mid-specimen surface between the notches and III(E) [N] is a
showing of a typical normal groove obtained during a valid
Accelerated Wear Test,
FIG. IV is a typical photographic plan view (2860 X) of an
electroless Ni-B alloy/9.mu. natural diamond composite indicating
the diagonal running test yarn course and showing structural
features as affected by the Standard Wear Test,
FIG. V is a typical photographic plan view (2640X) of an
electroless Ni-B alloy/9.mu. synthetic diamond "A" composite
indicating the running test yarn course and showing structural
features as affected by the Accelerated Wear Test,
FIG. VI is a typical photographic plan view (250X) of an
electroless Ni-B alloy/9.mu. synthetic diamond "A" specimen in the
as-plated condition (A) and after an Accelerated Wear Test (B),
FIG. VII is a typical photographic plan view (250X) of an
electroless Ni-B alloy/9.mu. natural diamond specimen in the
as-plated condition (A) and after an Accelerated Wear Test (B),
FIG. VIII is a typical photographic plan view (250X) of an
electroless Ni-B alloy/9.mu. synthetic diamond "B" specimen in the
as-plated condition (A) and after an Accelerated Wear Test (B),
FIG. IX is a sectional perspective view of a preferred embodiment
of apparatus which is employed to lay down the composite coatings
of this invention,
FIG. X is a fragmentary, cross-sectional, side elevation view of a
multi-filament yarn interlacing air jet which is advantageously
coated according to this invention,
FIG. XI is an end elevation view, partly in cross section, of a
multiplicity of interlacing jets of the design of FIG. X in
assembled relationship, and
FIG. XII is a section on line XII--XII, FIG. XI.
INTRODUCTION
The prior art is replete with publications teaching the
electroplating of metallic-diamond composite coatings; however, it
is believed that electroless plating of diamond composites has
never been successfully accomplished except, possibly, by the very
special technique taught in application Ser. No. 103,355, assigned
to common assignee, of which one of the present applicants is a
co-inventor. There is, it is true, art on the electroless plating
of composites of metals and particulate metal compounds,
specifically, British Pat. No. 1,219,813 (corresponding to U.S.
Pat. No. 3,617,363); however, there appears to be nothing with
respect to particulate diamond.
Applicants' composite laydowns must be distinguished from
electroless coating of diamond particles per se with nickel and
cobalt, such as taught in U.S. Pat. No. 3,556,839.
Applicants have now discovered a method of concurrently depositing,
by the electroless plating technique, as a disperse phase,
particulate diamond in composite with Ni(B), Ni(P), Co(B), Co(P)
and other metals and metal alloys singly, or as mixtures of any two
or more of these substances together, as well as metallic copper as
the continuous phase or matrix. The coatings produced are highly
adherent, relatively non-porous and possessed of a truly remarkable
abrasive wear resistance. In addition, the diamond particle
pull-out characteristics, particularly of the synthetic diamond
species "A" hereinafter described, are very good, so that
objectionable detritus is not carried over into the surrounding
environment which could, possibly, act as an abrasive agent to gall
or otherwise damage the fine finish of bearings or other
metal-to-metal contact surfaces. The combination of properties
displayed by the diamond composites of this invention are such that
they have great potential value as abrasion-resistant surfaces for
both dry and wet service, writing instrument nibs, cutting tool
surfaces, piston ring and other sliding contacting surfaces,
textile wear surfaces and other extremely demanding uses.
Applicants have prepared composites incorporating, singly,
particulate natural diamond and the only two synthetic diamonds
which are commercially available at the time of filing, these being
denoted synthetic diamond "A," which is explosively formed by
applicants' assignee in accordance with the teachings of U.S. Pat.
No. 3,401,019, and synthetic diamond "B," which is marketed by the
General Electric Company, Schenectady, N.Y., and which is believed
to be fabricated in accordance with the teachings of U.S. Pat. Nos.
2,947,608 through 2,947,611, inclusive.
As hereinafter described, the composites of applicant' invention
are usually used as relatively thin self-adhered coatings deposited
on the surfaces of a substrate consisting of a metal, polymer,
ceramic, glass, wood or other relatively rigid material. However,
if desired, the composites can be laid down on a temporary
substrate, such as thin metal, water-resistant paper, film or foil,
polymer sheeting or the like and the coating stripped therefrom (or
the temporary substrate melted or dissolved away) and thereafter
utilized as a wear-resistant shell per se, which can be adhered to
any firm supporting base material which is, in itself, suited to
the particular use environment's requirements, by adhesives,
cement, heat treatment or in other conventional manner known to the
art.
It is practicable to use a very wide variety of substrates and base
materials, the only limitation being that inherent in widely
different coefficients of thermal expansion as regards the coating
with reference to the underlying support material. Filled polymers,
such as those incorporating staple fibers as reinforcement, appear
to give most satisfactory substrate structures.
Applicants have prepared composite coatings on substrates of
unfilled ABS (acrylonitrile-butadiene-styrene copolymer), filled
ABS, ABS reinforced with glass fibers and with acicular TiO.sub.2,
polyimides, polyolefins, polyesters, "Delrin" acetal resins,
"Zytel" nylon resins, and "Nomex" aromatic polyamide resins, and,
while all have not been tested as thoroughly as some hereinafter
described, all have supported coatings that were visually uniform
and well-adhered.
Polymers are, of course, especially preferred in moderate
temperature corrosive service environments, because of their low
cost, relatively high resistance to corrosion and low contamination
potentiality. On the other hand, where relatively high temperatures
exist, or where it is necessary to improve the composite coating
properties by heat treatment, metals are preferred, since they
survive heating to relatively high temperatures without the warping
and compositional deterioration usually suffered by polymers.
THE DEPOSITION PROCESS
The composite deposition process employed in this invention can
utilize much of the published electroless plating art.
Thus, for electroless Ni-P alloy deposition U.S. Pat. Nos.
2,532,283, 2,658,841 and 2,658,842 are instructive. Similarly,
electroless Ni-B, Ni-Co-B, and Co-B processes are taught in U.S.
Pat. Nos. 3,062,666; 3,063,850; 3,096,182; 3,140,188; 3,234,031 and
3,338,726. Also, electroless Co-P and Ni-Co-P processes are
disclosed in U.S. Pat. Nos. 2,532,284 and 2,871,142. Finally,
electroless copper processes are described in U.S. Pat. Nos.
2,996,408; 3,075,855-6; 3,383,224; 3,431,120; 3,329,512; 3,361,580;
3,392,035; 3,457,089 and 3,453,123.
The electroless Ni-P processes which are the subjects of certain of
the Patents cited supra utilize aqueous solutions containing
H.sub.2 PO.sub.2.sup.- ions, which act as the reducing agent, and
nickel ions furnished by dissolved nickel salts. Similarly, the
electroless Ni-B processes utilize aqueous solutions of nickel
salts and a boron-containing reducing agent, such as BH.sub.4.sup.-
ions or dimethylamine borane (DMAB). In addition, workable
electroless plating baths contain buffers, e.g., salts of weak
carboxylic or dibasic acids, to prevent rapid changes in pH, plus
at least one of a large variety of chemical compounds or metallic
ions which act as stabilizers preventing spontaneous bath
decomposition.
The foregoing mentioned components, and others, are commonly
present in electroless plating baths, or are added during plating,
for such purposes as: (1) adjustment of pH, (2) complexing of metal
cations, (3) surface activity control, (4) bath efficiency control
and (5) deposit internal stress control, and these are generally
referred to herein as additives facilitating electroless plating
per se.
Among the patent references cited supra are several teaching that
other metallic or non-metallic elements, including (but not limited
to) lead, zinc, thallium and arsenic may be co-deposited with the
principal elements Ni, Co and Cu. It is also known that Ni, Cu and
P can be collectively co-deposited using a proprietary process of
the Shipley Company, Newton, Massachusetts.
More specifically, U.S. Pat. No. 3,140,188 teaches processes by
which Ni and Co can be deposited from stable baths containing Zn or
Fe, and that the coatings are smooth, adherent and constituted of
alloys including: Ni-Zn, Ni-Co-Zn, Co-Fe, and Ni-Fe. Also, U.S.
Pat. No. 3,062,666 teaches that a lead salt can be included in the
plating bath as a stabilizer, and it has been verified that the Ni
or Co plating from the bath of this Patent contains small
quantities of Pb, without impairing the smoothness. Similarly,
application Ser. No. 847,457, assigned to common assignee, teaches
that thallium can be a component of smooth, adherent electroless
plates if suitably incorporated in the bath. Moreover, U.S. Pat.
No. 3,063,850 teaches that not only Ni and Co but also Cu, Cd and
Sn individually can be plated as smooth adherent coatings by
electroless plating.
Accordingly, the instant invention is not limited to electroless
deposits consisting solely of the metals Ni, Co, Cu and the
non-metals P and B, but also comprises these elements singly and
plurally, as well as other elements whose presences are tolerable
or, indeed, beneficial, as far as bath stability and coating
quality are concerned.
Electroless plating is an autocatalytic process, in the sense that
the coating which is deposited serves as catalyst for continuation
of the plating process. Once plating is initiated on the surface of
a metallic, ceramic, polymeric or other substrate, it will continue
as long as the article remains in contact with the periodically
replenished plating solution. Since no electric current is required
for the plating which occurs, the general adjectives "electroless"
or "chemical" have been used to differentiate these processes from
conventional electroplating.
The diamond particles utilized in this invention can have
particulate sizes in the range of from less than about 0.1 to
50.mu. or even to 75.mu.. The quantity of diamonds incorporated in
our electroless alloy coatings can range from about 1 to about 50
volume percent.
The diamond particle shapes employed herein were approximately
equi-axed and there appeared to be no optimum particle size
distribution. Thus, the diamonds employed in some of the Examples
infra consisted of mixtures extending from about 1 to about 22.mu.
size.
In the plating of electroless alloy-diamond composites according to
this invention, a dispersion of diamond particles is maintained
throughout the plating bath, so that the particles constantly
contact surfaces of the substrates being coated. The plating baths
must be properly formulated, controlled and operated as hereinafter
described under conditions that prevent initiation of plating on
the surfaces of the diamond particles suspended in the bath. Thus,
if plating initiates on the surfaces of the suspended particles,
the bath will decompose by rapid depletion of the metallic ions and
the reducing agent, rendering the bath uncontrollable and useless
for further plating. The plated diamond particles which come into
contact with the substrates being coated form rough, highly porous,
nonadherent, unsightly deposits, which are totally unacceptable.
Thus, the object of our invention is completely different from that
of U.S. Pat. No. 3,556,839 and also of common assignee's
application Ser. No. 847,457, where the intent is to plate the
surfaces of the diamond particles suspended in the plating
bath.
Metallic substrates are given a conventional preplating treatment,
depending on the particular metal or alloy, prior to coating by
this invention. Thus, the steel specimens of the Examples infra
were first solvent-degreased in trichlorethylene, followed by hot
alkaline cleaning (e.g., Enbond S61) at 65.degree. C. for about 5
minutes, after which they were water rinsed, acid-etched in a 50%
by volume solution of HCl at room temperature for 30 to 60 sec.,
and water rinsed prior to immersion in the plating bath.
Plating initiates spontaneously on metallic substrates which are
catalysts for electroless plating processes. For example, for baths
that deposit nickel alloys, catalytic metals include Co, Ni, Pt and
Pd. Plating also initiates spontaneously on metals which are
noncatalytic but less noble than the bath metal, because a thin
film of the dissolved metal rapidly forms through displacement, and
the dissolved metal, being a catalyst, continues the plating
process. Examples of this, for electroless nickel processes, are
the plating of iron, aluminum, magnesium, beryllium and titanium.
Metallic substrates which do not initiate plating spontaneously can
be initiated galvanically by brief application of a small negative
potential to the substrate.
Nonconducting substrates, such as polymeric organic materials, are
prepared for plating by roughening mechanically as by grit blasting
(27 micron alumina being suitable), followed by a treatment
depositing a suitable catalyst for electroless plating, typically
immersion in an SnCl.sub.2 solution (70 g/l SnCl.sub.2 plus 40 cc/l
HCl, 80.degree. F.), water rinsing and immersion in a PdCl.sub.2
solution (0.1 g/l PdCl.sub.2 plus 1 cc/l HCl, 80.degree. F.) and
water rinsing. Pearlstein, in Metal Finishing, Aug. 1955, pp.
59-61, outlines a two-step approach to surface activation using the
hereinbefore described SnCl.sub.2 predip and PdCl.sub.2 activation
solution.
Numerous proprietary processes have been developed that combine and
simplify the individual steps of the activation procedures. For
example: (1) U.S. Pat. No. 3,563,784 teaches the preactivation step
of immersing plastic parts in a surfactant solution to insure
complete coverage with the electroless deposit of metal; (2) U.S.
Pat. No. 3,579,365 teaches the pre-etch preactivation step of
treating the polymer surfaces with colloidal or emulsified
fatty-acid materials to improve metal adhesion; (3) U.S. Pat. No.
3,562,038 and British Pat. No. 1,212,002 teach two approaches to
surface activation using colloidal suspensions of palladium
particles prepared by pre-reduction of palladium chloride with
stannous chloride. The foregoing processes extend the application
of electroless plating techniques to a wide spectrum of polymers,
including the polyolefins and polyesters.
Ni, Co PREPLATING TREATMENT
The ABS (i.e., acrylonitrile-butadiene-styrene copolymers), glass
fiber-reinforced ABS and acicular rutile fiber-reinforced ABS
resins described in the examples infra, which were given a plate
with diamond particles composited with electroless Ni and
electroless Ni-Co alloy matrices, were first given the following
preplating treatment.
1. Cleaning by immersion in a proprietary alkaline cleaner (e.g.,
Marbon C-15) for 5 minutes at 65.degree. C., to remove any grease
or oil picked up in molding or handling operations.
2. Rinsing in hot and cold water in the sequence recited for 30
secs. each.
3. Chemically roughening to promote coating adhesion by immersion
for 4-6 minutes at 65.degree. C. with mild agitation in a
proprietary chromic-sulfuric acid etch (e.g., Marbon E-20).
4. Rinsing in, first, hot and then cold water for 30 secs. each,
followed by an ultrasonic water rinse of 2 minutes and a final
rinse with running deionized water.
5. Sensitizing by immersion in a proprietary (Enplate 432) bath
containing tin ions with the parts agitated in the bath.
6. Rinsing twice in de-ionized water for 30 secs. each while
agitating gently to remove excess tin ions from the articles.
7. Immersing in a proprietary activation bath (e.g., Enplate - 440
) containing Pd ions. The tin ions were here oxidized under gentle
agitation for 1.5 minutes, thereupon reducing the Pd ions to
metallic state.
8. Finally, rinsing with two separate de-ionized water rinses of 30
secs. duration each while gently agitating.
COPPER PREPLATE
ABS reinforced and unreinforced specimens employed in the examples
infra, wherein particulate diamond was composited with an
electroless Cu matrix, were given the following preplating
treatment:
Steps 1 through 4 supra, then
5. Immersing in MacDermid, Inc. Metex PTH Activator 9070 at room
temperature for 8 mins.
6. Rinsing twice in de-ionized water for 30 secs. duration
each.
7. Immersing in Metex PTH Accelerator 9071 for 8 mins. at room
temperature.
8. Finally, giving the articles two de-ionized water rinses of 30
secs. duration each.
Ceramic substrates are prepared for plating by first mechanical
roughening, e.g., grit blasting, or by chemical roughening using an
aqueous HF solution to develop anchoring points for the catalyst
and for the wear-resistant electroless alloy strike that is
subsequently applied.
STRIKE TREATMENT
All of the specimens of the examples (except as described for Ex.
20) were given a 10 to 70 minute plating strike prior to plating in
the electroless alloy plating bath containing the diamond
dispersion. The strike bath was of the same composition as the
composite plating bath, except that it contained no diamond powder.
The purpose of the plating strike is to insure that the adhesion of
the initial electroless coating applied to the substrate is not
adversely affected by abrasive or other action of the dispersed
particles contained in the composite plating bath. A plating strike
is imperative in plating non-conductors such as polymers, ceramics,
wood and glass, the surfaces of which are thereby covered with
adsorbed layers or islands of a catalyst initiating electroless
plating. However, in the case of metallic substances displaying
high activity in the plating bath, e.g., plain C steel, Ni, Co and
Pd, the strike can be omitted.
The electroless alloy-diamond composite coatings of this invention
can be deposited by a wide variety of plating techniques ranging
from simple rack plating, wherein articles are supported by a rack,
to barrel plating, wherein the articles are introduced as free
bodies into a rotating bath container, which can have its axis
horizontally disposed or somewhat inclined. In addition, of course,
articles can be tumble-plated as taught in application Ser. No.
103,355 supra.
The diamond powder to be composited (0.5 to 100 gms. as desired) is
first blended with about 200 to 400 ml. of the plating bath in a
high-speed mixer to break up agglomerates, wet all of the particles
and form a concentrated slurry containing a uniform dispersion of
particles. The slurry is then slowly added to the plating vessel,
where the powder particles are kept in suspension by mechanical
agitation and/or bath circulation. The quantity of diamonds
maintained in the suspension, while most commonly in the range of 1
to 10 g. per liter of bath, can range up to as much as 40 g./liter,
the upper limit being only that the bath must remain sufficiently
fluid to be capable of ready agitation and circulation.
In the experiments hereinafter reported as examples, the metallic
ions, reducing agent and bath stabilizer were all replenished on a
periodic basis as determined by wet or colorimetric chemical
analyses for the respective reacting species.
RACK PLATER
One design of apparatus utilized in the preparation of specimens
for Examples 6, 7, 8, 19-22, and 26-28, inclusive, was the rack
plater shown somewhat schematically in FIG. IX of the drawings.
Referring to FIG. IX, the plating vessel 10 was a glass jar of 9
liters capacity, about 22 cm. inside diameter, which was provided
with two annular shelves 11 and 12, fabricated from
polytetrafluoroethylene, these shelves being held horizontal by
snug frictional through-bore mounting on three upstanding
polytetrafluoroethylene posts 16, only two of which appear in the
FIGURE.
Shelves 11 and 12 typically measured 13 cm. inside diameter, 20 cm.
outside diameter and were 0.6 cm. thick. Upper shelf 11 was
apertured at four locations 17 spaced 90.degree. apart
circumferentially, each sized to snugly engage a sample
approximately 0.635 cm. .times. 1.52 cm., so that the top and
bottom faces were exposed to the plating solution for the
simultaneous plating of these two surfaces. Lower shelf 12 was
provided on its upper face with a multiplicity of recesses 18,
which did not extend all the way through the shelf, these recesses
being dimensioned to closely fit the specimens 20, which were
snugly set therein, so that only the upper exposed surfaces were
plated.
An electric motor-driven stirrer (typically, 350 rpm) provided the
bath agitation, the shaft 22 of which was disposed approximately
concentric with the longitudinal axis of vessel 10, which stirrer
was provided, at its horizontally bent lower end, with an
upstanding elliptical paddle 23 having a major axis of 6.25 cm. and
a minor axis of 2.5 cm. The dimensions a, b and c denoted in FIG.
IX are, typically, 1.90, 2.54 and 7.62 cms., respectively.
EXAMPLES
General details as to the specimens prepared for typical individual
examples are provided in the following Tables:
Table 1A ______________________________________ Description of
Specimens in Examples on Plating Polymers
______________________________________ Recessed Samples.sup.1
Coupons.sup.2 Blocks.sup.3 Other Example FR- FR- FR- FR-ABS Number
ABS ABS ABS ABS ABS ABS Parts Total
______________________________________ 1 1 2 3 3 3 3 0 15 (TPC-40)
2 1 2 5 5 3 3 0 19 (TPC-32) 3 1 2 3 3 3 3 0 15 (TPC-39) 4 1 2 3 3 3
3 0 15 (TPC-36) 5 1 2 3 3 3 3 0 15 (TPC-46) 9 1 2 5 5 3 3 0 19
(TPC-33) 10 1 2 5 5 3 3 0 19 (TPC-34) 11 1 2 5 5 3 5 0 21 (TPC-28)
12 0 0 0 0 0 0 2 jet caps 2 13 1 0 0 6 1 1 6 venturi 15 (TPC-35)
units 14 0 0 1 1 1 1 0 4 (RPC-11) 15 1 2 3 3 3 3 0 15 (TPC-42) 16 1
2 5 5 3 5 0 21 (TPC-27) 17 1 2 3 3 3 3 0 15 (TPC-44) 18 1 2 3 3 3 3
0 15 (TPC-45) 23 1 2 5 5 3 3 0 19 (TPC-30)
______________________________________ Abbreviations: applicable to
Table 1A: TPC - Tumble-plated composites RPC - Rack-plated
composites ABS: acrylonitrile-butadiene-styrene FR-ABS:
fiber-reinforced acrylonitrile-butadiene- styrene
______________________________________ Footnotes: .sup.1 The
recessed-samples contained small diameter holes and slots. .sup.2
The dimensions of the coupons were 3 .times. 10 .times. 19 mm.
.sup.3 The dimensions of the blocks were 8 .times. 13 .times. 25
mm.
Table 1B ______________________________________ Description of
Specimens in Examples of Plating Steel
______________________________________ Number of Specimens Plated
______________________________________ Yarnline Example Wear Thrust
Number Blocks.sup.1 Block.sup.2 Washer.sup.3 Total
______________________________________ 6(RPC-6) 11 1 3 15 7 (RPC-7)
11 1 3 15 8 (RPC-12) 11 1 3 15 19 (RPC-3) 2 2 0 4 20 (RPC-20) 2 1 0
3 21 (RPC-21) 2 1 0 3 22 2 2 0 4
______________________________________ .sup.1 Dimensions of
rectangular blocks (6 mm .times. 10 mm .times. 15 mm .sup.2
Dimensions of rectangular yarnline wear block (6 mm .times. 6 mm
.times. 12 mm) .sup.3 Dimensions of cylindrical thrust washer:
Diameter: 31 mm Height: 9 mm
Table 1C ______________________________________ Weights of Samples
Plated ______________________________________ Individual Weights,
Designation & Material grams
______________________________________ "TP" samples 0.6 to 0.9 ABS
coupons 0.60 FR-ABS coupons 0.65 ABS blocks 2.6 FR-ABS blocks 3.2
Steel blocks 8.1 Steel yarnline wear block 3.6 Thrust washers 58
______________________________________
Table 1D
__________________________________________________________________________
Characteristics of Particulate Solids Incorporated Into Electroless
Coatings in the Several Examples
__________________________________________________________________________
Nominal Maximum.sup.1 Nominal Size Size % % Example Diamond or
Size, Range, Limit Over- Under- Numbers Other Powder .mu. .mu. .mu.
size size
__________________________________________________________________________
1,9,14, "A" 9 6 - 12 14 .about.3** .about.13** 15,19,20 2,10
natural 9 6 - 12 14 <5** <20** 3 "B" 9 6 - 12 14 <5**
<20** 4 .alpha.-Al.sub.2 O.sub.3 8 -- -- -- -- 5 .alpha.-SiC 6 1
- 10 None 20* 25* 6,8 "A" 1 0 - 2 3 .about.3** .about.13** 7
natural 1 0 - 2 3 <5** <20** 11,12,13 "A" 3 2 - 4 5
.about.3** .about.13** 16,17,18 "A" 5 2 - 8 None <10* <10*
21,25 "A" 6 4 - 8 10 .about.3** .about.13** 22 "A" 9 6 - 12 14
<5** <20** 23 "A" 17 12 - 22 None <15* <15* 24
.alpha.-Al.sub.2 O.sub.3 14 6 - 21 30 -- --
__________________________________________________________________________
.sup.1 No particle exceeded the maximum size limit when one is
specified. **Percentage of number of particles above upper limit of
nominal size range (oversize) or below lower limit of nominal size
range (undersize). *Weight per cent of powder above upper limit
(oversize) or below lower limit (undersize) of nominal size
range.
The plating process utilized in Examples 1-5, inclusive, was
identical, except that different types of powders were added to the
bath as indicated in the foregoing Table 1D. In each Example a
number (typically, 15-19) of molded ABS, glass-reinforced ABS, and
acicular rutile-reinforced ABS polymer articles were tumble-plated
as taught in application Ser. No. 103,355 supra, which is
incorporated herein by reference. (The acicular rutile is a powder
produced by the Pigments Department, E. I. Du Pont de Nemours Co.,
which consists of single crystals of TiO.sub.2 measuring about
0.2.mu. wide .times. 2 to 3.mu. long.) The plating was conducted in
an inverted frustoconical funnel of included angle 46.degree.
measuring 24 cm. in diameter across at the top end and 0.93 cm.
across the lower spout end, 25 cm. high, plating solution being
circulated continuously through the spout upwardly into the funnel
portion with overflow out of the top collected in a surrounding
sump. The plating solution velocity was maintained at a high enough
rate (typically 4,200 cm. 3/min.) to support the articles being
plated and, at the same time, tumble them slowly in a random manner
at a rate of 4 to 7 complete inversions per minute. However, the
tumble rate is a function of solution supply velocity, part size,
weight, shape and other factors, so that it varied somewhat over
the several Examples.
Two different sizes of articles to be plated were utilized, these
being (1) rectangular coupons measuring approximately 3 mm. .times.
10 mm. .times. 19 mm. and (2) rectangular blocks measuring 8 mm.
.times. 13 mm. .times. 25 mm.
The articles, contained in an open mesh, sieve-like, stainless
steel wire basket, were first given the pre-plating treatment
hereinbefore described and were then given a strike layer of Ni-B
alloy by immersion for about 10 mins. in a 4-liter beaker which
contained an electroless Ni-B plating bath (but no diamond
particles) of the composition:
______________________________________ Nickel acetate .4H.sub.2 O
50 g/l Sodium citrate .2H.sub.2 O 25 g/l Lactic acid 25 g/l
Dimethylamine borane (reducing 2.5 g/l agent) Thiodiglycolic acid
(stabilizer) 0.1 g/l Santomerse S (comm'l wetting agent) 0.1 g/l
NH.sub.4 OH (in quantity required to main- tain pH at 6.5) Water
Balance ______________________________________
The strike bath was maintained at a temperature of 55.degree. C.
The sample-containing basket was gently agitated. The specimens,
plated with a thin nickel strike, were then dumped from the basket
into the plating chamber of a tumble plater of the general design
described supra through which was flowed the same plating solution
as was used for the strike at a rate of approximately 4,200
cm.sup.3 /min. and plating was continued for about 1 hr. before any
particulate diamond additions. In Examples 1 through 4, in which 8
and 9.mu. classified size grades of powder (nominal size range
6-12.mu.) were used, the powder added was furnished in amount
sufficient to establish a concentration of suspended particles of 2
gm./liter of plating bath. In Example 5, in which a rough 1 to
10.mu. size grade of .alpha.SiC powder was used, the concentration
of powder added was increased to 3 gm./liter to establish a
concentration of particles in the 6 to 10.mu. size range
approximately equivalent to that of Examples 1 through 4. A
description of the type powder employed in each Example is reported
in Table 2. The period of composite plating was approximately 3.5
hours.
Table 2 ______________________________________ Description of
Powder Added to Tumble Plater
______________________________________ Example Particle No. Type
Structure Size ______________________________________ 1 synthetic
Fine-grained polycrystalline 9 diamond "A" particles 2 natural
Single crystal diamond cubic 9 diamond (ASTM x-ray data card No.
6-0675) 3 synthetic Single crystal diamond cubic 9 diamond "B"
(ASTM x-ray data card No. 6-0675) 4 .alpha.Al.sub.2 O.sub.3
Hexagonal (ASTM x-ray data 8 card No. 10-173) 5 .alpha.SiC (types
Hexagonal (ASTM x-ray data 1 to I & III cards No. 2-1463 and
2-1462, 10 mixed) respectively)
______________________________________
Metallographic examination of the composite coatings obtained in
Examples 1-5, inclusive, revealed that they appeared to be
nonporous and consisted of a uniform dispersion of the particulate
phase in the electroless Ni-B alloy matrix. Quantimet analysis was
used in all examples hereinafter described, to determine
particulate concentration in the coatings laid down. This employs
the Quantimet Image Analyzing Computer marketed by Metals Research,
Ltd., Hertz, England, using photomicrographs taken at preselected
magnification which indicated, for Examples 1-5, inclusive, that
about 10 vol. percent of the composite coatings consisted of
particles.
The samples were prepared for metallographic examination as
follows:
1. The coated surface was ground flat on 600 grit SiC abrasive
papers,
2. Rough polishing was then performed with 6-.mu. diamond abrasive
on hard-backed Pellon Pan W cloth,
3. Final polishing was then done for a short period with 0.05.mu.
Al.sub.2 O.sub.3 abrasive, taking care to avoid grinding through
the coating as well as avoiding excessive "rounding," and
4. Photographing at an appropriate magnification for epidiascopic
examination using the Quantimet image analyzing system as
indicated:
______________________________________ Particles
<3.mu.-photograph at .about.1500X 3 to 5.mu.-photograph at
.about.1000X >6.mu.-photograph at .about.500X
______________________________________
It was practicable to conduct metallographic examinations
successfully on wear test samples prepared as hereinafter
described, thereby saving double sample preparation.
The as-plated surfaces of the composite coatings were examined with
a scanning electron microscope (SEM) at magnifications ranging from
2,000X to 15,000X. Scanning electron photomicrographs, such as FIG.
I (6340X), showed the synthetic diamond "A" particles embedded in
the composite coatings plated in Example I largely by a nucleation
mechanism occurring at a number of different sites for each
particle. This is unique to diamond "A," as FIG. II for natural
diamond and many other photomicrographs (not reproduced here) for
synthetic diamond "B" show.
The reason for enhanced nucleation on synthetic diamond "A" is not
fully understood; however, the surface topography of diamond "A" is
so much rougher than that of natural diamond, and diamond "B,"
also, that it is believed this has a significant effect. Thus,
referring to FIG. I, diamond "A" is seen to have recessed growth
ledges (1), craters (2), upstanding growth projections (3) and a
multitude of other irregularities which appear to present optimum
sites for the nucleation of Ni-B alloy grains (4) on the diamond
surface per se. In addition, there exists a complete ring of Ni-B
nucleated grains around the edge of the diamond "A" particle. The
smooth, quite uniform Ni-B grain matrix existing outwards from the
diamond particles is relatively continuous and depressed for all of
the diamond particles, regardless of type.
Diamond "A" particles have a fine-grained polycrystalline
structure, being made up of a multitude of contiguous diamond
crystallites tightly bonded directly to one another in an
essentially unoriented pattern. The microstructure of diamond "A"
is characterized by a bimodal crystallite size distribution, single
coherent particles containing a population of very small, blocky,
variously oriented crystallites, typically having diameters in the
10-40 A range, interspersed with much larger blocky, unoriented
crystallites, typically having diameters in the 100-1600 A range,
and mean diameters in the 200-600 A range, as described in Belgian
Pat. No. 735,374 the Jl. Applied Physics, Vol. 42, pp. 503-510
(1971). The surfaces of these particles are irregular and of
relatively large area, e.g., a specific surface area of about 2 sq.
meters/gm., ideal for promoting nucleation of the matrix metal
thereon.
Nucleation of Ni-B grains on the diamond "A" surfaces is evidence
that chemical bonds form between the diamond and the alloy grains.
In addition, the Ni-B alloy grains cover all, or at least a major
portion of, the diamond surface, including under and around
projections, and around ledges, affording enhanced keying retention
of the diamond particles in the alloy.
Referring to FIG. II (6480X) for natural diamond, the sparseness of
nucleation (3) is clearly apparent, there being only a single small
nucleation growth at about 3 o-clock position. Thus, applicants'
research has shown that there is little or no nucleation growth
with respect to natural diamond and diamond "B," except where the
plating bath is on the verge of decomposition, under which
conditions the nucleation frequency is greatly enhanced. When a
plating bath can be operated under conditions approaching bath
decomposition, then plating can nucleate at many sites, even on
particles such as natural diamond and diamond "B," as they are
incorporated into the coating. (Refer Examples 26, 27, 28.)
Since natural diamond and synthetic diamond "B" both have a single
crystal structure, there are few crystal growth defects, such as
stacking faults, or macroscopic growth defects, such as ledges or
projections. SEM examination of the type represented by FIG. II,
reveals that both natural diamond and diamond "B" are characterized
by diamond surfaces which appear to be smooth and flat and
possessed of few ledge type defects. These smooth surfaces appear
to be cleavage planes of the diamond cubic system. Encapsulation of
the natural and diamond "B" particles takes place by outward growth
of Ni-B alloy grains from the catalytic sites of the original
substrate until they overlie the diamond, after which lateral
growth of the Ni-B alloy grains proceeds along with continued
outward growth. This type of growth can be confirmed, since at
times, after diamond laydown, one can, typically, observe, below
the level of the growing Ni-B alloy grains, a smooth diamond
surface about 1-5.mu. diameter remaining of the original diamond
particle expanse of about 9.mu.. This clearly indicates the lateral
growth of the Ni-B alloy grains slowly covering the smooth diamond
surfaces simultaneously with the continued outward growth of the
Ni-B grains.
Similarly, the typical structures shown in FIG. II for Example 2
has been found to exist also in Ni-P composites incorporating
natural diamond particles.
It should be understood that the nucleation and growth of
electroless alloy grains on catalytic surfaces is completely
different from that occurring with electrodeposited coatings. Since
nucleation and growth of metal or metal alloy grains depends, in
electroplating, upon the discharge of metal ions at a conductive
surface and, since diamond is non-conductive, there can be no
chemical bonding, only physical entrapment of diamond in an
electrodeposited matrix. In addition, the inclusion of
non-conductive diamond particles in an electrodeposited matrix
results in shielding of some metallic areas from any applied
potential. The shielded areas will either not plate at all, or will
at least plate at a slower rate than non-shielded areas, depending
upon the degree of shielding, which results in voids in the
coating. Voids do not occur in an electroless alloy/nonconductive
particle coating as long as there is suitable solution agitation
and movement of the article being plated. This movement and
agitation affords fresh metallic ions and reducing agent ingress to
all surfaces, at the same time voiding gaseous reaction products as
deposition proceeds.
An extremely important plating variable which requires control is
stabilizer concentration, and this is particularly true for diamond
"A."
In general, the stabilizer concentration must be high enough to
prevent spontaneous decomposition of the plating bath as well as
prevent nucleation of plating on the surfaces of the diamond
particles suspended in the bath. However, if stabilizer
concentrations is too high, nucleation of plating on the diamond
"A" particles that come into contact with, and are incorporated in,
the coating being deposited will be stifled. Indeed, excessively
high stabilizer concentrations poisons the electroless plating
reaction completely, even on a metallic surface which is normally a
catalyst for electroless plating, preventing the formation of any
coating whatever.
Experiments 16, 17, and 18 hereinafter reported, utilizing an
electroless Ni-B process stabilized with thiodiglycolic acid
(TDGA), show that the nucleation of plating on diamond "A"
particles is significantly inhibited at stabilizer concentrations
below those which completely poison the plating reaction on the
metallic matrix phase. Therefore, to achieve the unique attachment
of diamond "A" particles in the plating of electroless composite
coatings, the stabilizer concentration must be much more carefully
controlled than in conventional electroless plating. It is best
practice, in the electroless plating of diamond "A," to determine,
by experiment, the optimum stabilizer concentration for each
individual plating process as well as for each individual bath
stabilizer employed.
Other plating variables which affect the nucleation of plating on
all diamond types are pH, bath temperature and reducing agent
concentration. For each electroless alloy process, these variables
must be carefully controlled to achieve nucleation at multitudinous
sites on the diamond particles as these are incorporated into the
composite coating while, at the same time, preventing plating on
the particles suspended in the bath.
For the electroless Ni-B process of Example 1, the operating
temperature limits within which the desired nucleation will occur
are relatively broad, ranging from about 50.degree. C. to about
80.degree. C. At a temperature of above about 80.degree. C.,
plating starts to initiate on the diamond particles suspended in
the bath, causing it to decompose. On the other hand, at
temperatures below about 50.degree. C. nucleation of plating is
substantially inhibited. In addition, the effect of temperature on
abrasive wear resistance is shown by Examples 1 and 15. Thus
(Example 15), in a highly accelerated yarn line wear test, an
electroless Ni-B/9.mu. diamond "A" coating deposited at 40.degree.
C. (i.e., 10.degree. below the minimum level for best results),
where nucleation on the particles is stifled, had a wear rate of
9.6 .mu./hr. A comparable coating plated by the same process at
55.degree. C. (Example 1), where abundant nucleation occurs on the
incorporated diamond particles, had a wear rate of only 5.1
.mu./hr.
Some of the SiC particles in the coating of Example 5 showed
evidence of plating nucleation, but the number of nucleation sites
per particle was much less than that on diamond "A," Example 1.
WEAR TESTING
Since one very demanding abrasive service is yarn line processing,
two coating wear tests were developed using running yarn lines as
the abrading agents, the Standard Test being conducted with dry
yarn, whereas the Accelerated Test employed a yarn wet with an
abrasive slurry.
The specimens used in these tests consisted of coupons measuring
about 0.5 mm. wide cut from plated rectangular blocks measuring
about 8 mm. .times. 13 mm. in cross-section.
The procedure (Technique R) utilized for preparation of coated
polymer test specimens was as follows:
1. Sample mounted, in duplicate, in "Quick Mount" quick-setting
mounting resin,
2. Coated block sectioned with a hack saw perpendicular to the long
axis of the specimen,
3. Grind hack-sawed edge successively on 240, 400 and 600 grit SiC
abrasive papers, turning the specimen 90.degree. between steps,
4. Rough-polish the hack-sawed edge with 6.mu. diamond abrasive on
a hard-backed Pellon Pan W cloth,
5. Final-polish the hack-sawed edge with 0.05.mu. gamma Al.sub.2
O.sub.3 on a soft Micro-Cloth cloth,
6. Using a hacksaw cut approximately a 1/8 inch slice from this
mount parallel to the hack-sawed edge,
7. Mount this 1/8 inch slice on a stainless steel block with
two-sided tape, with the previously polished surface next to the
block,
8. Grind down outboard face to approximately 22 mils thickness with
240 grit abrasive paper,
9. Repeat steps 3 through 5, bringing to a final thickness of 18-20
mils, and
10. Remove the specimen from the stainless steel block using ethyl
alcohol or a similar solvent to soften the tape without damaging
the base material, and carefully peel the mounting medium from the
test piece.
The procedure (Technique S) utilized for preparation of coated
metallic wear test specimens was as follows:
1. Carefully clamp the coated metal specimen in a small, portable,
precision vice for sectioning with a wafer machine,
2. Align the vice so that the specimen long axis is perpendicular
to the SiC cutting wheel,
3. Slowly cut with two edge cuts to give a 30 mil slice from the
block,
4. Follow steps (3)-(5), inclusive, of Technique R for both cut
edge surfaces. Final thickness should be 18-20 mils, and
5. Etch in ethyl alcohol plus 4 vol. percent HNO.sub.3 for 2-5
secs. to delineate the coating-substrate interface.
The front and back surfaces of the test pieces were so smooth and
polished that 250X photomicrographs could be taken before and after
testing in order to evaluate the amount of wear. Photomicrographs
were also taken in plan of the surface of the coatings before and
after wear testing to distinguish between a valid test, where the
wear track extends across the entire width of the coating, and an
invalid test, where corner notching occurring at the front and/or
back edges is the result of localized edge cutting and the central
part of the wear track remains essentially untouched.
Both Tests employed the same general apparatus, shown schematically
in FIGS. IIIA-IIIC, except that only the Accelerated Test used the
slurry nozzle denoted at 28.
Test specimens were clamped in position during testing in a holder,
not shown, which was provided with sets of vertical ceramic pins in
front of and back of the specimen, which pins defined a vertical
slot normal to the width of the specimen about 0.25 mm. wide
through which the yarn line 29 ran. The yarn is drawn from a bobbin
(not shown) on the left side of FIG. 111A and is trained through
"pig tail" ceramic guides 30, through two sets of tensioning disks
31a and 31b, and thence under a 3.2 mm. diameter horizontal ceramic
pin 32 located 35 mm. in front of the central axis of the specimen
33. The yarn line next runs across the top coated surface 33a of
the specimen and leaves at a slight downward angle by transit under
3.2 mm. diameter horizontal pin 35 located 35 mm. downstream from
the central axis of the specimen. The vertical position of the
specimen can be adjusted by elevating screws or the like, not
shown, to preselect the break angle between running yarn 29 and the
horizontal plane of coated surface 33a.
STANDARD WEAR TEST
The Standard Test conditions adopted in Application Ser. No.
103,355 supra were used, these being as follows:
______________________________________ Yarn: 15-denier
monofilament, full dull nylon (Code designation 15-1-0-680D) (Merge
designation 15261) Yarn Tension: 10 gms. Yarn Speed: 1000 yds./min.
Break Angle: 5.degree. ______________________________________
Wear Rate in microns per hour was defined as the average depth of
the normal wear groove N, i.e., the sum of the wear grooves
measured in front, df, and back, db, respectively, divided by 2,
the whole divided by the test time in hours, as diagrammed for the
lower test track, FIG. IIIE. (Very accurate measurements of the
wear tracks were made from leading and trailing side elevation
(i.e., edge-on) photomicrographs under high magnification both
before and after each wear test.) Under the test conditions
described, the electroless Ni-P alloy with 9.mu. diamond "A"
composite coatings exhibited surface polishing but no measurable
wear even after 8 hours of continuous testing.
Increasing the severity of the test by increasing the tension to 15
gms. and the break angle to 10.degree. did result in some moderate
localized edge cutting (M) of the Ni-B, diamond "A" composite
coatings after 24 hours continuous testing; however, none of the
tests were valid because the central regions under the yarn track
were observed to be essentially unmarked (refer upper test track,
FIG. IIIE). The notches (M) cut in the edges of the coatings were
examined by scanning electron microscopy to ascertain differences
in wear mechanisms for comparable electroless alloy composite
coatings with different types of diamonds, the results of which are
hereinafter reported for individual Examples.
ACCELERATED WEAR TEST
An Accelerated Wear Test in which aqueous slurries of abrasive
particles were applied to running yarn line 29 was developed to
obtain quantitative wear measurements on our electroless alloy
diamond composite coatings. This utilizes a slurry applicator 28
between tensioning disks 31a, 31b and the first ceramic pin 32 as
shown in FIG. IIIA, i.e., 14.9 cm. ahead of the center line of
specimen surface 33a.
Applicator 28 was provided with an axial bore 28a a measuring 0.508
mm. dia. which opened into a vertical-sided end notch 28b 3.18 mm.
long, as measured in a horizontal plane in the direction of yarn
line travel. The base surface of notch 28b was a convex arc of
radius 1.58 mm. drawn from the vertical axis of the applicator. The
upper inner edges of notch 28b were beveled outwardly at slopes of
40.degree. measured from the vertical. The yarn line traversed the
orifice 28a diametrically at zero break angle, making essentially
tangent contact with the orifice lips. An abrasive slurry of oxide
particles dispersed in water was pumped through applicator 28 and
metered onto the yarn line. Initial scouting experiments were
conducted with slurries of 20 wt. percent pigmentary TiO.sub.2.
Subsequent work indicated that the severity of wear obtained with
slurries of 15% Linde A, .alpha.-Al.sub.2 O.sub.3, was much
greater. The relative severities of the tests run are compared in
Table 3, as to which the material tested was Vasco 7152, a tool
steel customarily used in the textile industry for severe abrasive
wear applications. Wear rate is expressed in terms of depth of
groove cut per unit time, i.e., .mu./hr., into the uncoated steel
coupon.
Table 3 ______________________________________ YARNLINE COMPARATIVE
WEAR TEST SEVERITY ______________________________________ Material
Tested: Vasco 7152 Tool Steel Yarn: 15-denier, monofilament full
dull nylon Yarn Speed: 1000 yds./min. Abrasive Slurry Feed Rate:
2.8 ml./min. for Test No. 3 and 2.5 ml./min. for Test No. 2. Yarn
Yarn Test Tension Break Abrasive Wear Rate, No. gms. Angle(Degs)
Slurry .mu./hr. ______________________________________ 1 15 10 None
2.4 2 10 10 0.7.mu. TiO.sub.2 280 in H.sub.2 O (conc'n 20 wt. %) 3
10 5 0.3.mu.Al.sub.2 O.sub.3 1450 in H.sub.2 O (conc'n 15 wt. %)
______________________________________
Under the circumstances, the conditions of test No. 3 were selected
for the Accelerated Wear Test for quantitative evaluation of the
electroless alloy diamond composite coatings. This test is severe
enough to cut grooves, or at least leave visible traces, in diamond
composite coatings which extend across the entire width of the test
samples, thereby permitting valid quantitative wear rate
determination. The test is also severe enough to rapidly cut
grooves in high density bulk Al.sub.2 O.sub.3.
A comparison of accelerated yarn wear test results for five
electroless Ni-B composite coatings containing particles about
9.mu. dia. of Al.sub.2 O.sub.3, SiC and three different types of
diamonds, Examples 1-3, respectively, is reported in Table 4. All
of the coatings reported were plated by the tumble plating process
of application Ser. No. 103,355 supra. Each contained about 10 vol.
percent of the particulate phase dispersed in the electroless Ni-B
alloy matrix.
Table 4 ______________________________________ ACCELERATED YARNLINE
WEAR TEST RESULTS Test Conditions: Same as Test No. 3 in Table No.
3 with a slurry feed rate of 2.8 ml./min.
______________________________________ Test Wear Example Time,
Rate, No Material min. .mu./hr.
______________________________________ 1 Electroless Ni-B/9-.mu.
Diamond 85 5.1 "A" Composite Coating 2 Electroless
Ni-B/9-.mu.Natural 85 10.2 Diamond Composite Coating 3 Electroless
Ni-B/9-.mu. Diamond 85 13.1 "B" Composite Coating -- Bulk 99.5%
Al.sub.2 O.sub.3 30 57 (Alsimag 785) 4 Electroless Ni-B/8-.mu.
Al.sub.2 O.sub.3 9 109 Composite Coating 5 Electroless
Ni-B/1-10.mu. SiC 5 278 Composite Coating -- Vasco 7152 Tool Steel
20 1,450 -- Electroless Ni-B As-plated 1/30 23,000 (with no
particles) ______________________________________
From Table 4 it can be seen that the three electroless Ni-B diamond
composite coatings are approximately a factor of 8 to 20 times more
wear-resistant than the Ni-B Al.sub.2 O.sub.3 composite coating and
approximately a factor of 20-55 times more wear-resistant than the
Ni-B(SiC) composite coating. The rate of abrasive wear for the
electroless Ni-B 9.mu. diamond "A" is approximately a factor of two
less than that of the comparable composites with natural diamond or
diamond "B." The superior wear resistance of electroless alloy
diamond "A" composite coatings demonstrated is attributable to the
strong chemical bond formed between the diamond "A" particles and
the electroless alloy matrix due to extensive nucleation of plating
on the diamond as hereinbefore described.
The effect of particle size and volume loadings on yarnline wear
resistance for electroless diamond composite coatings is apparent
from Table 5.
Table 5 ______________________________________ EFFECT OF PARTICLE
SIZE AND VOLUME LOADING ON YARNLINE WEAR RESISTANCE
______________________________________ Coating Matrix: Electroless
Ni-B alloy deposited by process cited in Example 1. Dispersed
Phase: Explosively formed diamond "A" Dispersed Phase Data Wear
Test Data ______________________________________ Example Average
Particle Volume, Time, Rate, No. Size, .mu. % min. .mu./hr.
______________________________________ 23 12-22 16 85 3.4 1 9 10 85
5.1 16 5 20 85 6.2 13 3 29 30 11.6 11 3 5 10 65 8 1 20 2 216
______________________________________
For the electroless Ni-B composite coatings of Examples 16, 13 and
8 the rate of abrasive wear increases from 6.2 .mu./hr. to 216
.mu./hr. as the average particle size decreased from 5.mu. to
1.mu.. The wear resistance of the coatings with particles about
3.mu. diameter is very sensitive to volume loading, as indicated
for Examples 11 and 13. The yarnline resistance for other types of
wear-resistant particles exhibit the same trends (directly
proportional to the loadings) with respect to the effects of
particle size and volume loading.
EXAMPLES 6 AND 7
Examples 6 (synthetic diamond "A" ) and 7 (natural diamond)
illustrate the differences in yarnline wear resistance of
electroless Ni-P alloy composite coatings containing 1.mu. diamond
"A" and 1.mu. natural diamond particles, respectively. In these
experiments plain carbon steel blocks were rack-plated in the
apparatus of FIG. IX hereinbefore described.
The fifteen steel blocks ranged in size from 6 mm. .times. 10 mm.
.times. 15 mm. to 6 mm. .times. 6 mm. .times. 12 mm. These were
given the conventional preplating treatment for steel supra, and
then immersed for 30 mins. in a Cuposit NL-63 electroless Ni-P
plating bath maintained at 85.degree. C. contained in the apparatus
22 cm. dia. jar. The blocks were disposed on lower shelf 12,
permitting coating of top and side surfaces; however, only the top
coating was wear-tested.
Then a slurry containing a preselected one of the types of
particulate diamonds supra in concentration to finally give 4 gms.
of powder per liter was slowly added. The stirrer was operated at
350.+-. 10 rpm to maintain a good powder dispersion in the plating
bath and the composite Ni-P alloy-diamond composites were laid down
for 3.5 to 4 hrs.
Specimens rack-plated as described contain a higher volume percent
of the diamond particulate phase in the horizontal top surface
coating than on the sides, and this was the surface chosen for wear
testing because the dispersion was most uniform.
Metallographic examination of the composite coatings of Examples 6
and 7 showed that both possessed a uniform dispersion of diamond
particles in the Ni-P alloy matrices. Quantimet analyses of
photomicrographs at 1800X showed that the composite coatings
contained about 20 volume percent of particulate diamond.
Results of accelerated yarnline wear tests conducted identically
with Examples 1 through 5 supra were as follows:
Table 6 ______________________________________ Test Wear Example
Time, Rate, No. Composite Coating Minutes .mu./hr.
______________________________________ 6 Electroless Ni-P/1.mu.
diamond "A" 2 378 7 Electroless Ni-P/l.mu. natural 2 732 diamond
______________________________________
Comparison of Example 6 with Example 7 shows that diamond "A" in
Ni-P matrix is superior to natural diamond in the same matrix.
EXAMPLE 8
Fifteen steel blocks were rack-plated with an electroless Ni-B
alloy composite coating containing one .mu. diamond "A" by the same
technique as employed for Examples 6 and 7, except that an
electroless Ni-B bath of the type of Example 1 was used. The blocks
were given a strike for 20 mins. before diamond addition.
The particulate diamond "A" (1.mu. size) was slowly added in an
amount establishing the final diamond concentration of the bath at
4 gm./liter, and composite plating was conducted at 55.degree. C.
for 4 hrs.
Again, metallographic examination of the top horizontal surface of
the blocks confirmed that there was a uniform diamond dispersion,
and Quantimet analysis indicated a 20 volume percent diamond
loading.
In a 2 minute accelerated wear test, conducted under identical
conditions as Examples 1, 6 and 7, the measured wear rate was 216
.mu./hr.
It was concluded that the Ni-B composite of Example 8 was
appreciably superior to the Ni-P composite of Example 6.
EXAMPLES 9 AND 10
These examples illustrate the differences in yarnline wear
resistance as a function of diamond type.
Examples 9 and 10 were, respectively, Ni-P alloy/9.mu. diamond "A"
and Ni-P alloy/9.mu. natural diamond composites laid down on
polymeric substrates.
For each Example, three blocks and five coupons were prepared from
ABS polymer, and the same from fiber-reinforced ABS. The blocks
measured 8.times. 13.times. 25 mm. and the coupons 3.times.
10.times. 19 mm. All pieces were tumble-plated as hereinbefore
described for Example 1.
All specimens were given the preplating treatment hereinbefore
described for ABS resins and were then coated as follows:
1. 10 mins. of electroless Ni-P strike in a Cuposit NL-61 bath
maintained at 65.degree. C. in a 4-liter beaker,
2. 60 mins. of tumble plating in a Cuposit NL-61 electroless Ni-P
bath maintained at 65.degree. C. in a tumble plater of the general
design taught in application Ser. No. 103,355 supra, and
3. 2.5 to 3 hrs. of composite tumble plating in Cuposit NL-61 bath
at 65.degree. C. containing a dispersion of 2 gm./liter of 9.mu.
diamond particles.
Metallographic examination of both types of the composite coatings
showed them to be possessed of a uniform dispersion of particulate
diamond in the electroless Ni-P alloy matrices. Quantimet analysis
at 750X revealed a particulate phase content of 23 volume
percent.
Scanning electron photomicrographs of the surfaces of the composite
platings of the Examples showed that there was extensive nucleation
of plating at multitudinous sites on the diamond "A" particles of
Example 9, whereas no nucleation was found in the case of the
natural diamond.
The results of accelerated yarnline wear tests on the composite
coatings are reported in the following Table 7, which also includes
Vasco 7152 tool steel as a comparison.
Yarn: 15-denier monofilament dull yarn
Yarn Speed: 1000 yds./min.
Yarn Tension: 10.+-. 2 gms.
Yarn Break Angle: 5.degree.
Abrasive Slurry: 15 wt. % Linde A Al.sub.2 O.sub.3 in H.sub.2 O
Slurry Feed Rate: 2.4.+-. 0.2 ml./min.
Table 7 ______________________________________ Test Wear Example
Time, Rate, No. Composite Coating Minutes .mu./hr.
______________________________________ 9 Electroless Ni-P/9.mu.
diamond 90 3.3 "A" 10 Electroless Ni-P/9.mu. natural 80 7.5 diamond
Vasco 7152 Tool Steel 20 1040
______________________________________
Conclusion: Diamond "A" is definitely superior as regards wear
resistance.
EXAMPLE 11
Rectangular blocks and coupons of molded ABS and fiber-reinforced
(some glass fiber and some acicular rutile employed singly) ABS
resins were given the polymer pretreatment hereinbefore described
for ABS resins and were then coated by the following procedure:
a. 10 minute strike in a 4-liter beaker by the electroless Ni-B
process of Example 1,
b. 1 hr. of tumble plating by the electroless Ni-B process of
Example 1 in a bath free of particle additions, and
c. 3 hrs. of composite tumble plating by the electroless Ni-B
process of Example 1 in a bath containing a dispersion of 2 g./l.
of 3.mu. diameter diamond "A" particles.
Metallographic examination of the composite coating obtained
confirmed that it was non-porous and possessed of a uniform
dispersion of the diamond particles in the Ni-B alloy matrix.
Quantimet analysis of photomicrographs taken at 500X showed a
particulate phase loading of about 5 volume percent. Scanning
electron photomicrographs of the surface of the composite coating
showed evidence of the nucleation of plating at a multitude of
sites on individual incorporated diamond particles.
In a 10 minute accelerated yarnline wear test conducted under
conditions identical to those described for Examples 1 through 5
the wear rate was 65 .mu./hr. Refer to Table 5 for comparative
performance.
EXAMPLE 12
Referring to FIGS. 9 and 10 of U.S. Pat. No. 3,279,164, there is
shown a yarn processing jet which comprises two mating portions, a
"cap" and a "body," which are separable for convenience in
stringing up yarn, disassembly taking place at approximately
section 10--10, FIG. 9, with the cap itself resembling the design
of FIG. 10. The cap was machined from a block of ABS resin filled
with 15% of acicular rutile.
The cap was tumble-plated to give an electroless Ni-B/3.mu. diamond
"A" composite coating by the procedure employed in Example 11,
except that, in order to obtain only a thin coat, the deposition
time was decreased to 80 minutes. Upon inspection under a low power
microscope, it was observed that the narrow passageways in the cap
were plated similarly to the flat faces which, of course, is
important, because the major wear occurs in the passageways.
A test was made using this plated cap in the processing of 18
denier, three-filament nylon yarn running at a rate of 400
yds./min. for a period of 1 hour. No observable effect was noted on
the quality of yarn twisted in this jet as compared with a normal
tool steel jet. Inspection of the passageways of the cap after the
test completion failed to reveal any evidence of abrasive wear.
Scanning electron photomicrographs of the surface of the composite
coating showed evidence of nucleation of plating at numerous sites
on the individual incorporated diamond particles.
The utility of the composite coating in this practical application
was thus demonstrated.
EXAMPLE 13
Two jet venturi units of the design disclosed in U.S. Pat. Nos.
2,852,906, 3,545,057 and 3,577,614 were machined from molded,
acicular rutile-reinforced ABS rods. The jet venturi units, plus an
assortment of molded ABS and fiber-reinforced ABS rectangular
blocks and coupons, were simultaneously plated with an electroless
Ni-B composite coating containing 3.mu. diameter diamond "A" by the
following process:
All articles were first given the hereinbefore described preplating
treatment for ABS resins and were then coated as detailed:
a. 10 min. strike in a 4-liter beaker by the electroless Ni-B
process of Example 1.
b. 1 hr. of tumble plating by the electroless Ni-B process of
Example 1 in a bath free of particle additions, and
c. 2.67 hrs. of composite tumble plating by the electroless process
of Example 1 in a bath containing a dispersion of 8 gm./liter of
3.mu. diamond "A" particles.
Metallographic examination (200X) of the composite coatings
confirmed that the coating was non-porous and possessed of a
uniform dispersion of diamond particles in the electroless Ni-B
alloy matrix.
Quantimet analysis of photomicrographs taken at 1000X magnification
indicated that the coatings contained about 29 volume percent of
particulate diamond. Scanning electron photomicrographs of the
surfaces of the composite coatings showed evidence of nucleation of
plating at multitudinous sites on individual incorporated diamond
particles.
In a 30 minute accelerated yarnline wear test conducted as
described for Examples 1 through 5, inclusive, the wear rate on the
electroless Ni-B/3.mu. diamond "A" coating was 11.6 .mu./hr.
The two polymeric jet venturi units plated with electroless
Ni-B/3.mu. diamond "A" composite coatings were assembled into
completed jets. Other jets were assembled with acicular
rutile-reinforced ABS venturi units plated with electroless Ni-B
alloy as taught for Example 1.
All of the jets were subjected to processing 70 (total denier)/34
(number of filaments) Type 56 and 70/50 Type 62 polyester yarns.
The yarn wore completely through the coating on the inner surfaces
of the venturi units plated with electroless Ni-B alloys (without
diamond) after less than 80 hrs. of processing. The inner surfaces
of the venturi units plated with the electroless Ni-B/3.mu. diamond
"A" coating showed no signs of abrasive wear after 150 hrs. of
continuous processing.
EXAMPLE 14
This example illustrates the unique attachment between explosively
formed diamond "A" and an electroless Cu matrix deposited by
McDermid, Inc.'s Metex RS Copper 9055 process.
Molded rectangular blocks of ABS and fiber-reinforced ABS resins
were given the preplating treatment hereinbefore described for
nonconducting substrates generally and were then immersed in an
electroless Metex RS copper 9055 bath maintained at 50.degree. C.
in a 4-liter beaker. The blocks, which were suspended from copper
wires, were positioned about 5 cm. from the bottom of the beaker at
locations spaced around the periphery. Plating of electroless
copper (free of diamond particles) ensued for about 1 hr. Then a
slurry of plating bath plus a sufficient quantity of 9.mu. dia.
diamond "A" particles to establish a concentration of 2 gm.
powder/liter of plating bath was added to the beaker. The plating
bath was agitated with a powered stirrer operated at a speed
sufficient to keep the powder particles in suspension. Composite
plating in the presence of diamond particles was conducted for 5
hrs.
The resulting Cu/9.mu. diamond "A" composite showed moderate
nucleation of copper grains with the diamond "A." The copper matrix
was composed of 1 to 4.mu. grains which displayed a crystal-like
growth mechanism, i.e., all surfaces intersected at the same
angles, which appeared to be approximately 90.degree.. The
nucleated copper grains on the 9.mu. diamond "A" particles
displayed the same type of crystal-like growth mechanism as the
copper grains in the matrix. Copper grains as small as 0.4.mu. were
observed on the diamond "A" particles, thus being similar to Ni-B
grains nucleated on 12.mu. diamond "A" particles (refer FIG.
I).
It was thus demonstrated that a copper-diamond composite could be
made which is at least superficially as uniform as the
nickel(B)alloy-diamond composites. Also, since the nucleation was
similar in extent, the diamond "A" particles appeared to be
well-anchored.
EXAMPLE 15
This example illustrates the effect of plating bath temperature on
the nucleation of plating on explosively formed diamond "A"
particles incorporated into electroless alloy composite coatings,
and on the wear resistance of these coatings.
Electroless Ni-B alloy composite coating containing 9.mu. dia.
diamond "A" particles were plated by the process of Example 1,
except that the bath temperature was decreased from 55.degree. to
40.degree. C.
Rectangular blocks and coupons of molded ABS and fiber-reinforced
ABS resins were first given the hereinbefore described pretreatment
required for ABS resins and were then coated as follows:
a. 10 min. strike in a 4-liter beaker by the electroless Ni-B
process of Example 1 at 55.degree. C.,
b. 1 hr. of tumble plating by the electroless Ni-B process of
Example 1 at a temperature decreasing from 45.degree. C. to
40.degree. C., at the end, and
c. 3.75 hrs. of composite tumble plating by the electroless Ni-B
process of Example 1 in a bath containing 2 gm./liter of 9.mu. dia.
diamond "A" particles, the bath being maintained at 40.degree.
C.
Metallographic examination of the composite coatings confirmed that
the coatings were possessed of a uniform dispersion of 9.mu. dia.
diamond particles in the electroless Ni-B alloy matrix. Quantimet
analysis of photomicrographs taken at 500X of the surfaces of the
composite coatings showed approximately 9% concentration of
particulate phase.
Scanning electron photomicrographs of the surfaces of the composite
coatings showed nucleation of plating on only about 10% of the
diamond particles incorporated therein, and these particles had
only one or two nucleation sites per particle.
In accelerated yarnline wear tests conducted as described for
Example 1, the wear rate on the electroless Ni-B/9.mu. diamond "A"
composite coatings plated at 40.degree. C. was 9.6 .mu./hr. This
wear rate is almost a factor of two greater than that for a
comparable Ni-B/9.mu. diamond "A" composite coating plated at
55.degree. C., which exhibits nucleation of plating on
multitudinous sites around each diamond particle.
EXAMPLES 16, 17 AND 18
These examples illustrate the effect of stabilizer concentration
and plating bath temperature on the nucleation of plating on
diamond "A" particles incorporated into electroless alloy composite
coatings, and on the wear resistance of these coatings. In these
experiments electroless Ni-B alloy composite coatings, each
containing a range from about 2 to 8.mu. diameter diamond "A"
particles were plated as in Example 1 at stabilizer concentrations
of thiodiglycolic acid (TDGA) ranging from 0.10 to 0.20 gm./liter
and a temperature ranging from 50.degree. to 55.degree. C. as
indicated in Table 8.
Rectangular blocks and coupons of molded ABS and fiber-reinforced
ABS resins were given the standard polymer ABS pretreatment
hereinbefore described and then coated as follows:
a. 10 min. strike in a 4-liter beaker by the electroless Ni-B
process of Example 1,
b. 15 to 60 mins. of tumble plating using the bath composition of
Example 1, except as modified in Table 8 infra in a bath free of
particle additions, and
c. 3 to 4 hrs. of composite tumble plating using the bath
composition of Example 1, except with 2 gm./liter of the 2 to 8.mu.
dia. diamond "A," and excepting also as modified in Table 8
infra.
Table 8 ______________________________________ BATH COMPOSITIONS
AND CONDITIONS ______________________________________ TDGA Plating
Example Stabilizer Conc., Temp Rate, No. Content gm./liter .degree.
C. .mu./hr. ______________________________________ 16 Standard
(same as 0.10 55 5.3 Example 1) 17 High TDGA, otherwise 0.20 55 4.6
same as Example 1 18 High TDGA and low 0.20 50 2.9 temperature,
other- wise same as Example 1
______________________________________
The coatings of Examples 16, 17 and 18 were possessed of a uniform
dispersion of diamond particles in the electroless Ni-B alloy
matrix, as determined by metallographic examination. Quantimet
analysis showed approximately 20 volume percent of particulate
phase in the composite layers.
The results of accelerated yarnline wear tests on the composite
coatings and observations made during SEM examination are listed in
Table 9. The wear test conditions were identical to those for
Examples 1 through 5. SEM photomicrographs of the composite
coatings plated in baths with high TDGA concentration (i.e.,
Examples 17 and 18) show no evidence of nucleation at a multitude
of sites on the diamond "A" particles. These coatings exhibited a
significantly higher wear rate than composite coatings deposited in
the standard bath at a TDGA concentration of 0.10 gm./liter, i.e.,
Example 16.
Table 9
__________________________________________________________________________
Weat Test Data
__________________________________________________________________________
Scanning Electron Micro- Wear Example Stabilizer scopy Observations
on Time, Rate, No. Content Composite Coatings Mins. .mu./hr.
__________________________________________________________________________
16 Standard Majority of diamond particles 85 6.2 incorporated
nucleated plat- ing at a multitude of sites on their surfaces. 17
High TDGA Only about 10% of the par- 85 7.8 ticles incorporated had
nucleation, and these had only one or two nucleation sites per
particle. 18 High TDGA Only about 10% of the par- 60 8.4 and Low
ticles incorporated had Tempera- nucleation, and these had ture
only one or two nucleation sites per particle.
__________________________________________________________________________
EXAMPLE 19
Steel blocks were rack-plated with an electroless Ni-Co-B alloy
composite coating containing 9.mu. diamond "A" particles by the
technique used for Example 6 supra.
The blocks were mounted on shelf 12 of the plating apparatus of
FIG. IX, given a conventional preplating treatment for steel and
then immersed in an electroless Ni-Co-B plating bath of the
following composition:
______________________________________ Nickel acetate .4H.sub.2 O
44 gms/liter Cobaltous acetate .4H.sub.2 O 6 gms/liter Sodium
citrate .2H.sub.2 O 25 gms/liter Lactic acid 25 gm/liter
Dimethylamine borane 2.5 gm/liter Thiodiglycolic acid 0.1 gm/liter
Santomerse S 0.1 g/liter NH.sub.4 OH in quantity required to
maintain pH at 6.4 Water Balance
______________________________________
The plating bath was maintained at 60.degree. C. and the blocks
were plated with an electroless Ni-Co-B strike for 20 mins. Then a
slurry containing a sufficient quantity of 9.mu. dia. diamond "A"
to establish a concentration of 2 gms/liter was introduced into the
plating bath. The diamond particles were kept in suspension by a
mechanically-driven, paddle-type stirrer rotating at about 350 rpm.
Plating was conducted for 3 hours.
The composite top surface coatings obtained were given a
metallographic examination and it was found that a uniform
dispersion of diamond particles existed throughout the Ni-Co-B
matrix.
Quantimet analysis of photomicrographs of the same surface
disclosed that the coating contained about 11 volume percent of the
particulate phase, and scanning electron photomicrographs revealed
nucleation of plating at multitudinous sites on individual diamond
particles incorporated into the surface.
In an 85 minute accelerated yarnline wear test, conducted under the
identical conditions for Example 1, the wear rate was 4.2
.mu./hr.
Conclusion: A Ni-Co-B matrix/diamond "A" composite coating appears
to be at least as wear-resistant as the Ni-B/diamond "A" composite
coating of Example 1.
EXAMPLE 20
Steel blocks were rack-plated with an electroless Ni-P alloy
composite coating containing 9.mu. dia. diamond "A" particles by
the technique described supra for Example 6 using Enthone, Inc.'s
Enplate NI-415 process.
The steel blocks were mounted on shelf 12 of the apparatus of FIG.
IX, given the conventional pretreatment for steel, and then
immersed in an Enplate NI-415 bath and given a 30-min. strike at
85.degree. C. Then a suspension of 9.mu. diameter diamond "A"
particles was added to give 1 gm/liter and plating continued. The
diamond powder was maintained in suspension by a mechanically
driven, paddle type stirrer rotated at about 350 rpm. The blocks
were removed from the bath after 1.5 hrs. of composite plating.
Metallographic examination of the composite coating on the top
horizontal surface of the steel blocks showed a uniform dispersion
of the diamond particles in the electroless Ni-P matrix. The
coating was found to contain about 32 vol. percent of the
particulate phase.
In an 85 minute accelerated wear test conducted as hereinbefore
described for Example 1 the measured wear rate was 3.8 .mu./hr.
A second set of steel blocks was rack-plated as hereinbefore
described for the first set of steel blocks of this Example, except
that the 30-min. strike was omitted, and the appearance and diamond
content obtained was the same. It is concluded that, with a metal
substrate, a strike is not always necessary.
EXAMPLE 21
Steel blocks were rack-plated with an electroless Co-B alloy
composite coating containing 6.mu. dia. diamond "A" by the
technique described for Example 6 supra.
The bath employed had the following composition:
______________________________________ CoSO.sub.4 7H.sub.2 O 25 g/l
(NH.sub.4).sub.2 SO.sub.4 60 g/l Sodium citrate .2H.sub.2 O 40 g/l
Dimethylamine borane 2.5 g/l NH.sub.4 OH in amount maintaining pH
at 7.5 Water Balance Bath temperature 80.degree. C
______________________________________
The blocks were first given an electroless Co-B strike for 25 mins.
Then a slurry containing 6.mu. dia. diamond "A" was added to give a
plating bath concentration of 1 g/l, the diamond particles being
kept in suspension by a power-driven paddle-type stirrer. Composite
plating in the presence of diamond was done for 105 mins.
Approximately five minutes after the steel blocks were removed, the
bath decomposed due to excessive plating on the diamond particles
suspended therein.
Metallographic examination of the composite coating on the top
horizontal surface of the blocks confirmed uniform dispersion of
the diamond particles within the Co-B matrix, and the diamond
concentration was measured at 25 volume percent. Scanning electron
microscope photomicrographs showed nucleation of plating at
multitudinous sites on individual diamond particles incorporated in
the coating.
A wear test specimen was sliced from a plated block using a
wafering machine provided with a 10 cm. dia., 1.2 cm. thick SiC
cutting disk driven at 6500 rpm by a 1/3 HP motor. An aqueous
solution of Johnson Wax Co's. T.L.-131 cutting fluid was sprayed on
the disk as coolant. Portions of the coating became detached and
flaked away from the substrate at several locations on the top
horizontal surface of the steel substrate, indicating that the
coating adhesion was unsatisfactory. None of the other plated steel
specimens of the other Examples exhibited coating detachment when
similarly cut, except for those specimens of Examples 27 and 28,
which were also plated from an active bath which exhibited a
tendency to decompose.
An accelerated yarnline wear test was conducted in an area free
from coating dislodgement under the conditions hereinbefore
reported for Example 1. In an 85 minute test, the wear rate was 3.2
.mu./hr.
EXAMPLE 22
Steel blocks were rack-plated with an electroless Co-P alloy
composite coating containing 9.mu. dia. diamond "A" by the
technique of Example 6.
The blocks were first given the conventional preplating treatment
for steel and then immersed in an electroless Co-P plating bath of
the following composition:
______________________________________ CoCl.sub.2 6H.sub.2 O 30 g/l
NH.sub.4 Cl 50 g/l Sodium citrate .2H.sub.2 O 80 g/l NaH.sub.2
PO.sub.2 H.sub.2 O 10 g/l NH.sub.4 OH in quantity maintaining pH at
9 Water Balance Plating bath temperature 90.degree. C
______________________________________
The blocks were plated with an electroless Co-P strike for 50 mins.
Then sufficient 9.mu. dia. diamond "A" was slowly added to
establish a concentration of 0.5 g/l, the particles being kept in
suspension by a power-driven paddle-type stirrer. Composite plating
in the presence of diamonds was continued for 4 hours.
SEM photomicrographs reveal that nucleation of electroless Co-P
alloy did not occur on the diamond "A" particles incorporated in
the coating.
EXAMPLE 23
Rectangular blocks and coupons of molded ABS and fiber-reinforced
ABS resins were given the polymer pretreatment hereinbefore
described for ABS resins and were then coated by the following
procedure:
a. 10 min. strike in a 4-liter beaker by the electroless Ni-B
process described for Example 1,
b. 1 hr. of tumble plating by the electroless Ni-B process
described in Example 1 in a bath free of particle additions,
and
c. 3 hrs. of composite tumble plating by the electroless Ni-B
process described for Example 1 in a bath containing a dispersion
of 2 g/l of 12-22.mu. dia. diamond "A" particles.
SEM photomicrographs of the composite coating surface revealed that
nucleation of plating had occurred at a multitude of sites on
individual incorporated diamond particles. The coating contained
about 16 vol. percent of particulate phase.
In an 85 minute accelerated yarnline wear test conducted as
described in Example 1, the measured wear rate was 3.4 .mu./hr.
EXAMPLE 24
Rectangular blocks and coupons of molded ABS and fiber-reinforced
ABS resins were given the polymer pretreatment hereinbefore
described for ABS resins and were then coated by the following
procedure:
a. 10 min. strike in a 4-liter beaker by the electroless Ni-B
process employed in Example 1,
b. 1 hr. of tumble plating by the electroless Ni-B process employed
in Example 1 in a bath free of particle additions, and
c. 32/3 hrs. of composite tumble plating by the electroless Ni-B
process described for Example 1 in a bath containing a dispersion
of -600 mesh .alpha.-Al.sub.2 O.sub.3 powder.
Metallographic examination of the composite coating showed it to be
nonporous and possessed of a uniform dispersion of Al.sub.2 O.sub.3
particles throughout the electroless Ni-B alloy matrix. The coating
contained 11 volume percent of the particulate phase. The size of
the majority of the Al.sub.2 O.sub.3 particles observed in the
photomicrographs ranged from about 6.mu. to about 21.mu..
In a 5 minute accelerated yarnline wear test conducted as described
for Examples 1 through 5, the wear rate on the electroless
Ni-B/6-21.mu. Al.sub.2 O.sub.3 was 161 .mu./hr., which is more than
47 times greater than that for the comparable electroless
Ni-B/12-22.mu. diamond "A" coating described for Example 23.
EXAMPLE 25
A steel block was rack-plated with an electroless Co-B alloy
composite coating containing 6.mu. dia. diamond "A" particles in a
1-liter bath stored in a 2 liter glass beaker 12 cm. in
diameter.
The block was suspended from a nickel wire, given a conventional
preplating treatment for steel and then immersed in an electroless
Co-B plating bath of the following composition:
______________________________________ CoCl.sub.2.6H.sub.2 O 30 g/l
Sodium citrate .2H.sub.2 O 80 g/l NH.sub.4 Cl 50 g/l Dimethylamine
borane 2.5 g/l NH.sub.4 OH in amount maintaining pH at 8-9 Water
Balance Plating bath temperature 90.degree. C.
______________________________________
The block was first plated with an electroless Co-B strike for 85
minutes. Then the bath temperature was increased to 95.degree. C.
and a slurry containing enough 6.mu. dia. diamond "A" particles to
establish a concentration of 0.5 g/l was added to the plating bath
and kept in suspension by a power-driven paddle-type stirrer.
Composite plating in the presence of diamond particles was
continued for 2.5 hrs. The bath showed no signs of
decomposition.
SEM photomicrographs revealed that no nucleation of electroless
Co-B alloy occurred on the diamond "A" particles incorporated in
the coating.
The conclusion drawn from Examples 21, 22 and 25 is that bath
composition can affect whether or not nucleation of electroless
alloy grains will occur on diamond "A" particles.
Thus, Example 21 showed that a Co-B/6.mu. diamond "A" composite
coating from a bath formulated with CoSO.sub.4.7H.sub.2 O did have
nucleation, whereas, in Example 25, the Co-B/6.mu. diamond coating
formulated from a CoCl.sub.2.6H.sub.2 O bath did not show
nucleation, nor did the Co-P/9.mu. diamond "A" coating of Example
22.
EXAMPLE 26
Steel blocks were rack-plated with an electroless Ni-Co-B alloy
composite coating containing 9.mu. diameter natural diamonds by the
same technique and plating process and bath composition described
for Example 19.
Scanning electron micrographs revealed nucleation of plating at a
multitude of sites on individual diamond particles incorporated
into the coating on the top horizontal surface of the blocks. This
was the first indication of nucleation at numerous sites on natural
diamond.
The results of accelerated wear tests and determination of volume
percent particulate loading for this coating, and the Ni-Co-B/9.mu.
diamond "A" coating reported in Example 19 are as follows:
______________________________________ Test Wear Vol % Time, Rate,
Coating Particles min. .mu./hr.
______________________________________ Example 19 Ni-Co-B/9-.mu.
diamond 11 85 4.2 "A" Example 26 Ni-Co-B/9-.mu. Natural 37 85 5.5
diamond ______________________________________
Between Example 1, and Examples 19 and 26, two changes were made:
(1) The temperature was raised from 55.degree. C. to 60.degree. C.
and (2) 6 gm/liter of nickel acetate was replaced by 6 gm/liter of
cobalt acetate. As a result of these two changes, nucleation took
place on natural diamond as well as on diamond "A" during their
incorporation into the coating.
EXAMPLES 27 AND 28
Steel blocks were rack-plated with an electroless Ni-Co-B/9.mu.
natural diamond composite coating (Ex. 27) and an electroless
Ni-Co-B/9.mu. diamond "A" composite coating (Ex. 28) by the same
technique as described for Example 19.
This process differed from that used in Example 19 and in Example
26 in four ways:
1. TDGA concentration was increased from 0.10 to 0.14.
2. The Santomerse S wetting agent concentration was decreased from
0.1 g/l to zero.
3. The concentration of diamond "A" powder in the bath was
decreased from 2 g/l to 1 g/l.
4. The temperature of the bath was increased from 60.degree. C. to
65.degree. C.
NOTE: The reason the bath temperature was increased was because the
plating rate at 60.degree. C. was considered to be too low.
The bath used in Example 28 decomposed after 5 hrs. of operation
due to initiation of plating on the diamond "A" particles suspended
in the plating bath.
Scanning electron micrographs of the top horizontal surfaces of
plated steel blocks show much nucleation on both the diamond "A"
particles incorporated into the coating in Ex. 28 and the natural
diamond particles incorporated into the coating in Ex. 27.
Conclusions:
The Ni-Co-B baths hereinbefore described are excessively active, in
the sense that they will readily initiate plating on powder
particles added to them. When particles with high-energy surfaces,
such as diamond "A" are added to them, they can decompose due to
initiation of plating on the suspended particles which rapidly
depletes the bath of metallic ions and reducing agent. When
particles with low-energy surfaces, such as natural diamonds, are
added to these "active" baths, plating initates on the particles as
they are incorporated into a composite coating being deposited on a
substrate.
EXAMPLE 29
Electroplate v. Electroless Plate
A comparison was made between diamond-containing electroless Ni-P
coatings and diamond-containing electroplated nickel coatings.
Various samples were prepared to permit comparison, these being
plain steel, an alumina-containing electroless Ni-P plate, and
solid sintered tungsten carbide in a cobalt matrix. The tests were
carried out on a Dow-Corning Corp. Model LFW-1 "Alpha" Friction and
Wear Testing Machine. The essential mechanism of the test is the
rubbing of a lubricated rotating ring against the surface of a
specimen under constant applied load. After a predetermined number
of revolutions of the ring, the specimen was inspected, and the
volume worn away by the rotating wheel was calculated. The test
parameters were:
1. Test Ring: 4620 steel, Rockwell C (Rc) 62
2. Test Block: 4620 steel, Rc 62 (also used as substrate for coated
samples)
3. Normal Load: 150 lbs.
4. Mean Hertzian Stress: 55,000 psi
5. Testing Speed: 197 rpm (71 ft/min. sliding velocity)
6. Test Duration: 250,000 revolutions
7. Lubricant: SAE 10 oil
The relative wear-resistance of the specimens when normalized
around the performance of an uncoated 4620 steel block was as
follows, it being understood that increasing values denote
progressively greater wear resistance.
______________________________________ 4620 Steel, Rc 62 1.00
Aluminum oxide/Ni-P (electroless)* 1.00 Natural diamond/Ni-P
(electroless)* 2.74 Diamond "A"/Ni (electroplated)* 4.98 Diamond
"A"/Ni-P (electroless)* 6.83 Sintered tungsten carbide (12% Cobalt)
11.58 ______________________________________ *Composite coatings
containing 20 volume % hard particles, 1 -micron size
The "electroless" samples in the above list were prepared according
to the same detailed manner as in Examples 6 and 7, supra. The
"electroplated" sample was prepared by a commercial nickel
electroplating firm, using sample blocks of 4620 steel substrate
and diamonds furnished. The tungsten carbide sample was a piece of
commercial material.
EXAMPLE 30
It as been found that concomitant particulate solids-electroless
plate coating according to this invention is not only effective for
interrecess coating but also preserves the integrity of sharp edges
in structures where sharp edges are essential for good
operation.
The importance of uniform surface maintenance inside jets and
orifices, together with retention of uniform sharp edge
configurations at jet and orifice outlets, is discussed in fluid
dynamics texts such as, for example, Chapters 5 and 6 of "Mechanics
of Fluids" by Glenn Murphy, published by International Textbook
Company.
Referring to FIGS. X-XII, inclusive, one design of jet coated
successfully according to this invention is the air jet utilized
for interlacing multi-filament textile yarns, as taught in U.S.
Pat. No. 3,115,691.
As shown in FIG. X, an interlacing apparatus can utilize two air
jets 51 of typical diameters in the range of about 0.020 to about
0.10 inch inclined towards one another at an angle .alpha. of,
typically, 60.degree., so that their center lines approximately
intersect at a striker plate 49 disposed, typically, 0.008-0.120
inch from the jet housing. A multi-filament yarn 56 is passed
centrally of the jets and the inside face of striker plate 49a, as
shown, and is interlaced by the action of air vortices created by
the jets. It should be mentioned that interlacing whips the yarn
about quite violently and there occur repeated yarn impacts with
the face of jet body 50 as well as across the jet orifices.
It has been found that jet-to-jet passage uniformity as well as
sharp and true opening edge uniformity is extremely critical to
interlacing yarn jet performance. Thus, coating build-up as shown
at E and F, FIG. X, which almost always occurs to some degree
during such operations as plasma and flame spray coating, even
though the holes may be sealed by removable polymeric plugs such as
a silicone resin, is absolutely prohibitive. In addition, chipped
edges such as denoted at G which sometimes result when polymer
plugs are disengaged, cannot be tolerated. Thus, the standard of
acceptance required is a sharply defined edge, such as that shown
at H.
It is extremely inconvenient and disruptive of production to
periodically recondition textile interlacing jets, since a
multiplicity are assembled together with their housings 50 in
parallel connection with a common air manifold 53 via port 55.
As shown in FIG. XI, it is convenient in such assemblies to utilize
the back sides of neighboring jets as striker plates 49 for
adjoining jets 51 directed towards them. Screws 52 secure
individual jets into a tight module, whereas machine screws 54
attach the modules to the manifold casing 53.
In this Example, 12 interlacing jets of the construction
hereinbefore described were molded from an acicular rutile
reinforced ABS resin. These jets measured 1.14 inch short length
.times. 1.18 inch long length and had discharge openings 0.036 inch
diameter. They were plated with an electroless Ni-B 3.mu. diamond
"A" composite coating using the following procedure:
The jets were first given the hereinbefore-described preplating
treatment for ABS resins and were then coated as detailed:
a. 10 min. strike with gentle agitation in a 4-liter beaker by the
electroless Ni-B process of Example 1.
b. 22 min. of tumble plating by the electroless Ni-B process of
Example 1 in a bath free of particle additions.
c. 72 min. of composite tumble plating by the electroless process
of Example 1 in a bath containing a dispersion of 8 g/l of 3-.mu.
diamond "A" particles.
The coating procedure was identical to that cited in Example 13 for
plating jet venturi units, except that the total plating time was
decreased from 230 to 104 min. The plating time was decreased to
minimize coating thickness and thereby retain the edge sharpness at
the exit orifices of the air holes in the jets. As hereinbefore
stated, sharpness and uniformity of the air orifices are important
parameters that affect jet performance and yarn quality.
Photomicrographs and scanning electron micrographs of the jet
orifices revealed that they were well coated on the interior and
uniform, with sharp edges free of defects. The radius of the
orifice edge was increased only by an amount comparable to the
total coating thickness, which was about 0.4 mils. The scanning
electron micrographs also revealed that the coating consisted of a
uniform dispersion of 3.mu. diameter diamond particles in an
electroless Ni-B matrix. The surface roughness in the as-plated
condition ranged from 40 to 60 AA (i.e., arithmetic average).
A test as conducted with the plated plastic interlace jets in which
70-denier/34-filament R-25-285 nylon yarn was interlaced for a
period of 72 hours. The yarn was of acceptable quality and
interlace level. Characterization by scanning electron microscopy
and surface profilometry of critical areas on the surfaces of the
jets after testing failed to reveal any evidence of abrasive
wear.
By way of comparison, a Vasco 7152 Tool Steel, such as hereinbefore
described with reference to Table 3, shows a relatively high wear
rate.
EVALUATION OF WEAR TEST RESULTS
The wear grooves of the electroless alloy/diamond composites were
not only measured to determine wear rate but were also studied to
determine the strength of bonding of the particulate diamond within
the coating matrix for each of the three diamonds tested, i.e.,
diamond "A," diamond "B" and natural diamond. Thus, the wear
grooves were carefully examined by scanning electron microscopy and
light microscopy to determine the types of wear suffered and, also,
whether diamond pull-out occurred under thread-line abrasion.
Referring to FIG. IV (2860X), it is clear that extensive diamond
pull-out occurred for the electroless Ni-B alloy/9.mu. natural
diamond composite coating under a 24 hr. 15-denier full dull nylon
monofilament yarnline test wherein the yarn speed was 1000 yd./min.
at 15 gms. tension and 10.degree. break angle. The fact that the
areas indicated by arrows (1) in FIG. IV are particle pull-outs can
be confirmed by comparing the crater shapes with the shapes of the
natural diamond particles (3) remaining in the matrix. In general,
the standard yarnline wear test showed a considerable number of
natural diamond particle pull-outs from the Ni-B alloy matrix,
whereas essentially no pull-outs were observed in an identical
standard test evaluation of Ni-B alloy/9.mu. diamond "A"
composites.
This is dramatically shown in FIG. V (2640X), taken after an
accelerated yarnline test, wherein the wear scar (1) of the running
yarnline is plainly seen, without, however, any particle loss
craters.
Additional light microscopy examinations of accelerated yarnline
wear tests for composites containing 9.mu. diamond "B" particles
confirmed the superior wear resistance of the composites containing
diamond "A," which showed little wear groove polishing action.
In contrast, FIG. VI, a 250X microscopic plan view of the entire
wear sample width, shows the wear groove (2) of the same diamond
"A" composite shown in localized magnification in FIG. IV. The
corresponding views for the 9.mu. natural diamond particle
composite (FIG. VII) and the diamond "B" composite of FIG. VIII
show the extensive matrix metal-polishing action which occurs in
both of these yarnline wear tracks during yarnline testing. This is
due to the cutting action of the 0.3.mu. .alpha.Al.sub.2 O.sub.3
particles on the threadline, which removes the electroless alloy
matrix. The majority of matrix removal occurs after particle
pull-out.
An attempt was made to obtain a quantitative comparison of particle
pull-out magnitudes for the three diamond types. In this, an SEM
montage at .apprxeq.1400X of (a) the bottom and (b) one side of the
wear groove along with a portion of as-plated surface adjoining the
wear groove. An area 12 inches .times. 1.5 inch (Area I) was then
outlined on the as-plated surface and side of the wear groove of
each montage such that the outlined area contained about half of
each region. A similar 12 inches .times. 1.5 inch area (Area II)
was then outlined on the bottom of the wear groove such that one of
the 12 inches sides of Areas I and II was common. The number of
diamonds and diamond craters was then counted to give a total as
received diamond count for each Area. The number of diamond craters
was essentially zero for Area II, the bottom of the wear groove,
for all three types of diamonds; however, a number of craters were
seen to exist in Area I of the natural and diamond "B" composites,
whereas the diamond "A" composite Area I showed essentially zero
craters. The results obtained are as follows:
Table 10 ______________________________________ DIAMOND PULL-OUT
FROM ACCELERATED YARNLINE WEAR TEST GROOVES (Ni--B Alloy Composite
prepared by Ex. 1-3 techniques)
______________________________________ Per Cent Area Area Differ-
I* II** ence Comments ______________________________________
Diamond Count 50 34 - 32% Difference for Diamond primarily due to
"B" diamond removal Diamond Count 60 45 - 25% from the bottom for
Natural of the wear Diamond grooves Diamond Count 42 46 + 9.5%
Difference due to for Diamond randomness and un- "A" covering of
diamonds on the bottom of the wear groove which were just under the
surface of Ni--B alloy matrix.
______________________________________ *Side of wear groove and
adjacent as-plated composite surface. **Bottom of wear groove, area
where the majority of wear occurs.
In appraising the results tabulated, it is estimated that
approximately 2-6% error might exist due to the coexistence of
matrix multi-grain depressions which can possibly be mistaken for
craters, depending on the extent of the polishing concealment
effected by the running yarn passage.
The significance of the comparison portrayed by FIGS. VI, VII and
VIII is, of course, that not only is the surface wear substantially
greater for natural diamond and diamond "B" composites than for
diamond "A," but that the detritus removed from the coatings is at
the same time markedly higher. Such detritus, incorporating, as it
does, diamond particles, becomes an intolerable contaminant if
retained in the wear region vicinity, as would be the case with a
bearing or other similar installation wherein the contacting
surface is not being swept clean continuously by an agency such as
the running yarnline employed in the tests described.
From the foregoing, it is apparent that the diamond "A" particles
are much more firmly secured within the metal matrix than are the
diamond "B" and natural diamond particles. It is assumed that this
superior retention is due to the fact that diamond "A" particles
are able to promote nucleation and matrix grain growth when they
are at the matrix surface growing region .
* * * * *