U.S. patent number 3,916,506 [Application Number 05/407,656] was granted by the patent office on 1975-11-04 for method of conforming a flexible self-supporting means to the surface contour of a substrate.
This patent grant is currently assigned to Mallory Composites. Invention is credited to Jack D. Wolf.
United States Patent |
3,916,506 |
Wolf |
November 4, 1975 |
Method of conforming a flexible self-supporting means to the
surface contour of a substrate
Abstract
A method of conforming a flexible self-supporting means to the
surface contour of a substrate and articles made by the method. In
the method of coating a wear resistant material over an intricate
surface contour of a substrate, it is important that the wear
resistant material be substantially uniformly distributed over the
surface contour thereof, and that the coating be metallurgically
joined to the surface contour. The method includes the steps of
providing a flexible self-supporting means including wear resistant
powder and a powdered material to serve as a matrix material with a
heat decomposable organic binder, then overlaying the surface
contour of the substrate with the means, causing the means to
substantially conform to the intricate surface contour of the
substrate, and heating the means to a temperature below the
decomposition temperature of the organic binder to relieve stresses
in the means created by conforming it to the surface contour of the
substrate. Alternatively, the means may be heated prior to
conforming it to the surface contour, or simultaniously with
conforming it to the surface contour to relieve the aforementioned
stresses. Preferably, the step of causing the means to conform to
the intricate surface contour of the substrate includes the
application of pressure to the means.
Inventors: |
Wolf; Jack D. (Indianapolis,
IN) |
Assignee: |
Mallory Composites
(Indianapolis, IN)
|
Family
ID: |
23612981 |
Appl.
No.: |
05/407,656 |
Filed: |
October 18, 1973 |
Current U.S.
Class: |
428/457; 428/145;
228/122.1; 428/148; 428/698 |
Current CPC
Class: |
B23K
35/0244 (20130101); C23C 24/10 (20130101); Y10T
428/24388 (20150115); B23K 35/0238 (20130101); Y10T
428/31678 (20150401); Y10T 428/24413 (20150115) |
Current International
Class: |
C23C
24/00 (20060101); C23C 24/10 (20060101); B23K
35/02 (20060101); B23K 031/02 () |
Field of
Search: |
;29/472.9,472.5,473.1,475,478,481,482 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Al Lawrence
Assistant Examiner: Joyce; Margaret M.
Attorney, Agent or Firm: Hoffmann; Charles W. Meyer; Robert
F. Hanson; Donald W.
Claims
I claim:
1. In a method of coating a substrate with a wear resistant
material including wear resistant powder and a matrix material, the
matrix material being the product of a flowing powdered material
having a melting point temperature lower than the melting point
temperature of the wear resistant powder, the method including the
steps of providing a flexible self-supporting means including the
wear resistant powder and the powdered material to serve as a
matrix material in a heat decomposable fibrillated organic binder,
overlaying the substrate with the flexible self-supporting means,
causing the flexible self-supporting means to substantially conform
to the contour of the substrate, and heating the flexible
self-supporting means to a temperature below the decomposition
temperature of the fibrillated organic binder to relieve stresses
in the flexible self-supporting means caused by conforming the
flexible self-supporting means to the contour of the substrate.
2. In the method of claim 1, the further step of, after conforming
the flexible self-supporting means the surface contour of the
substrate, treating the fibrillated organic binder to remove the
binder and causing the powdered material to flow into intersticies
between and wet the surface contour of the substrate and
solidifying the flowable material to provide a wear resistant
coating including powdered wear-resistant material and a matrix
material.
3. In the method of claim 2, wherein the wear resistant powder is
selected from the group consisting wear resistant alloys, diamond,
tungsten carbide, tantalum carbide, chromium carbide, titanium
carbide, silicon carbide, tungsten boride, tungsten silicide,
tantalum silicide, chromium silicide or titanium silicide,
preferably tungsten carbide or chromium carbide, and wherein the
matrix material is selected from the group consisting of iron based
alloys, nickel based alloys or cobalt based alloys, preferably a
nickel based alloy.
4. In a method of claim 2, including the further step of, prior to
treating the fibrillated organic binder to remove it, treating the
flexible self-supporting means to cause it to adhere to the surface
of the substrate.
5. In the method of claim 4, wherein the step of treating the
flexible self-supporting means includes providing the means with an
adhesive between it and the substrate.
6. In the method of claim 1, wherein the step of causing the
flexible self-supporting means to substantially conform to the
substrate further includes applying pressure to the flexible
self-supporting means.
7. In the method of claim 6, wherein the fibrillated organic binder
is fibrillated polytetrafluoroethylene which entraps the
particulate filler and matrix substance, the organic binder being
about 0.5 to about 10 volume % of the flexible self-supporting
means.
8. An article of manufacture having a wear resistant surface made
according to the method of claim 2.
9. In the method of claim 1 wherein the step of heating the
flexible self-supporting means to relieve stresses is done either
prior to or simultaneous with the step of causing the flexible
self-supporting means to conform to the contour of the substrate.
Description
The present invention relates to a method and to an article
produced by that method wherein a flexible self-supporting means is
conformed to an intricate surface contour of a substrate to be
coated with a wear resistant material. The flexible self-supporting
means is caused to conform to the intricate contour of the surface
of the substrate, and then heated to a temperature below the
decomposition temperature of a heat decomposable organic binder
incorporated in the self-supporting means to relieve stresses in
the means created by conforming it to the contour of the substrate.
Alternatively, the means may be heated prior to conforming it to
the surface contour, or simultaneously with conforming it to the
surface contour to relieve the aforementioned stresses. Preferably,
the step of causing the flexible self-supporting means to conform
to the intricate includes the application of pressure to the
self-supporting means.
U.S. Pat. No. 3,743,556 granted to E. J. Breton et al. discloses a
method of coating a substrate with a wear resistant coating
including wear resistant powder dispersed in a metal matrix. In an
example given in the patent, a flexible sheet containing a mixture
of polytetrafluoroethylene and powdered tungsten carbide is made by
ball milling and then pressing the ball milled mixture between
pressure rolls to provide a flexible sheet having a thickness of
about 30 mils. Another flexible sheet containing a mixture of
polytetrafluoroethylene and a powdered nickel based material is
made by ball milling and then pressing the ball milled mixture
between pressure rolls to provide a flexible sheet having a
thickness of about 20 mils. A surface of a substrate to be coated
with wear resistant material is overlayed with the sheet containing
the powdered tungsten carbide and then that sheet is overlayed with
the sheet containing powder nickel based material to form a
laminate of sheets. The laminate of sheets is heated to a
temperature in a neutral or reducing atmosphere which causes
decomposition and volatilization of the polytetrafluoroethylene of
both sheets and flowing of the nickel base material to
metallurgically wet the powdered tungsten carbide and
metallurgically wet the surface of the substrate to provide a
substrate with a wear resistant metallurgically bonded coating
including tungsten carbide in a nickel based matrix.
Using the techniques disclosed in U.S. Pat. No. 3,743,556, it is
difficult to coat a surface of a substrate having an intricate
contour such as acute and/or obtuse angle joints. In the event
there is little close contact between the surface of the substrate
to be coated and the liminate of sheet material, discontinuities in
the resultant coating of wear resistant material tend to result
which may have a harmful effect on the wear resistant
characteristics desired of the coating. One suggestion is to cut
sections of sheet into the desired configuration and adhere such
sections of sheet to the intricate surface contour in an attempt to
conform sheet material to the surface contour. Production
difficulties manifest themselves when one attempts to handle a
multiplicity of small pieces of cut sheet to be used in coating a
surface of a substrate.
It was found that the above problems could be minimized by
conforming the self-supporting means to the contour of the surface
to be coated and heating the means, either prior to, simultaneous
with, or subsequent to conforming to the surface to be coated, to a
temperature below the decomposition temperature of the organic
binder to permit the means to relieve stresses caused by conforming
the means to the surface contour of the substrate. The means is
then subjected to a temperature sufficient to remove the organic
binder and cause the powdered material to metallurgically wet the
wear resistant powder and function as a matrix material, and to
metallurgically wet the surface of the substrate. Preferably,
pressure is used to conform the means to the surface contour of the
substrate.
Accordingly, it is a feature of the present invention to provide a
method of conforming a self-supporting means containing powdered
metal containing material with an organic binder to the surface of
a substrate prior to treating the self-supporting means to remove
the organic binder. Another feature of the present invention is to
provide a method of causing a self-supporting means including metal
containing material with an organic binder to conform to an
intricate surface contour of a substrate by the application of
pressure, and heating the means to a temperature below the
decomposition temperature of the organic binder to relieve stresses
in the means created by conforming the means to the surface contour
of the substrate. Other features will be apparent from the
following detailed description and claims.
In the drawing:
FIG. 1 is a side view of a substrate having an intricate surface
contour overlayed with the flexible self-supporting means; and
FIG. 2 is a front view of the substrate illustrated in FIG. 1
overlayed with the flexible self-supporting means.
Generally speaking, the method of the present invention relates to
coating a surface of a substrate with wear resistant powder in a
metal matrix that wets the wear resistant powder and
metallurgically bonds to the surface of the substrate. The matrix
material has a melting point temperature lower than the melting
point temperature of the powdered wear resistant material and the
substrate. The method includes the steps of providing a flexible
self-supporting means including the powdered wear resistant and
powdered material to serve as a matrix material with a heat
decomposable organic binder. The substrate is overlayed with the
flexible self-supporting means, caused to conform to the surface
contour of the substrate, and heated to a temperature of the
organic binder to help relieve stresses created in the means by
conforming it to the surface contour of the substrate. Preferably,
pressure is applied to conform the self-supporting means to the
contour of the surface of the substrate.
U.S. Pat. No. 3,743,556 teaches a method for making the
self-supporting means including decomposable organic binder, wear
resistant powder and a powdered metal which is intended to serve as
a matrix material. The teachings of the patent relating to a method
of making the self-supporting means are incorporated herein by
reference.
Powdered wear resistant material and powdered material to serve as
a matrix material are mixed with powdered polytetrafluoroethylene.
The mixture is mechanically worked to cause the
polytetrafluoroethylene to fibriliate to entrap and retain
particles of both powdered materials. The resultant self-supporting
means has good handleability and drapeability characteristics.
The fibrillable polytetrafluoroethylene used in the method is
commercially available in a molecular weight range of about 10 to
20 million. Preparation of polytetrafluoroethylene useful in the
present invention is described in U.S. Pat. No. 2,510,112, U.S.
Pat. No. 2,587,357 and U.S. Pat. No. 2,685,707. The average
particle size of such polytetrafluoroethylene is up to about 500
microns or more. However, polytetrafluoroethylene having a larger
average particle size or a smaller average particle size of down to
50 microns or less is useful in making the flexible self-supporting
means. Polytetrafluoroethylene used in the fibril containing
self-supporting means is sold by E. I. duPont de Nemours &
Company of Wilmington, Del. as Teflon 6, 6C, 6H and 3264.
The powdered material contained in the self-supporting sheet
material that may serve as a matrix material includes ceramics,
metals, metal containing compounds, plastics and the like. The
matrix substance appears in the self-supporting sheet material in
powdered form. The average particle size of the powdered matrix
material can vary widely. The average particle size of the powdered
matrix material may be as small as a few microns up to 100 microns
or larger. The powdered material, in order to function as a matrix
material, must have a melting point temperature less than the
melting point temperature of the powdered wear resistant material,
and must be capable of metallurgically wetting both the surface of
the substrate to be coated and then powdered wear-resistant
material. Preferably, the powdered material which is to function as
the matrix material of the coating is selected from metal alloys
including iron based alloys, nickel based alloys or cobalt based
alloys, and most preferably the powdered material is a nickel based
alloy. Typical nickel based alloys useful are self-brazing alloys
selected from the group of ASTM BNI-1 thru ASTM-BNi-7.
The powdered wear resistant material useful in providing wear
resistant coatings includes wear resistant alloys, diamond,
tungsten carbide, tantalum carbide, chromium carbide, titanium
carbide, silicon carbide, tungsten boride, chromium boride,
titanium boride, silicon boride, tungsten silicide, tantalum
silicide, chromium silicide, titanium silicide and the like. The
average particle size of the wear resistant material may be as
small as 10 microns or up to 50 microns or larger. The powdered
wear resistant material, in order to function as a wear resistant
material, must be highly wear resistant and must be metallurgically
wetted by the matrix material of the coating. Preferably, the wear
resistant material of the coating is either tungsten carbide or
chromium carbide. Generally, tungsten carbide is employed in use
situations where good wear resistant characteristics are required.
Chromium carbide is employed in use situations requiring high
temperature resistance and in conventional grinding situations.
The amount of pressure required to conform the flexible
self-supporting means to the intricate surface contour of the
substrate to be coated varies in proportion to the amount of heat
needed to relieve the stresses created in the self-supporting
means. Generally speaking, the greater the pressure used to conform
the means to the surface contour the less temperature required to
relieve stresses in the means. For example, if about 30 to 70
pounds per square inch are exerted against the means to conform it
to the contour of the surface to be coated, the temperature of the
means should be raised to about 90.degree.C to about 325.degree.C
to relieve stresses created in the means by conforming it to the
surface contour of the substrate. The preferred temperature range
for relieving stresses in the conformed self-supporting means is
about 175.degree.C to about 200.degree.C. Note that the temperature
range is below the decomposition temperature of
polytetrafluoroethylene.
Preferably, pressure to conform the self-supporting means to the
surface contour of the substrate to be coated is applied through a
surface complimentary with the surface of the substrate to be
coated. Such a complimentary surface may be provided in a number of
ways. One presently preferred complimentary surface is provided by
a thick, flexible sheet of polyurethane attached to a rigid backing
means.
The following example illustrates a specific embodiment of the
method of the invention.
EXAMPLE
A self-supporting sheet with tungsten carbide is made in the
following manner: 95 volumes of 10 micron tungsten carbide powder
is ball milled with 5 volumes of polytetrafluoroethylene (DuPont 6C
Teflon) for 30 minutes. The ball milled mixture is pressed between
pressure rolls to provide a sheet. The rolled mixture is rotated
90.degree. and rerolled. The rotation of the sheet 90.degree. and
re-rolling is repeated until a self-supporting sheet of about 20
mils to 50 mils in thickness is provided.
A self-supporting sheet with a nickel based alloy of ASTM BNi-1 is
made in the following manner: 95 volumes of 10 micron ASTM BNi-1 is
ball milled with 5 volumes of polytetrafluoroethylene (DuPont 6C
Teflon) for 30 minutes. The ball mixture is pressed between
pressure rolls to provide a sheet. The rolled mixture is rotated
90.degree. and rerolled. The rotation of the sheet 90.degree. and
rerolling is repeated until a self-supporting sheet of about 20
mils to 50 mils in thickness is provided.
A surface 10 of a substrate 11 is heated to a temperature of about
175.degree.C. A self-supporting sheet 12 with tungsten carbide and
fibrillated polytetrafluoroethylene is placed contiguous to the
surface 10 of the substrate 11 to be coated with a wear resistant
coating (not shown). The sheet 12 may be coated with a suitable
adhesive such as shellac and the like. Substrate 11 is a plain
carbon steel. The self-supporting sheet 13 with ASTM BN-1 and
fibrillated polytetrafluoroethylene is overlayed the
self-supporting sheet 12. The laminate of sheets 12 and 13 provides
a flexible self-supporting means 14. A complimentary surface (not
shown) is brought in contact with the self-supporting means 14 to
apply sufficient pressure to cause the means 14 to conform to the
surface contour 10 of the substrate 11. The complimentary surface
is withdrawn leaving behind self-supporting means 14 conformed to
the intricate surface contours of substrate 11. The heated surface
10 of the substrate 11 relieves stresses created in the means 14 by
conforming it to the contour of the surface of the substrate.
The substrate 11 with the conformed, self-supporting means 14 is
heated in a hydrogen atmosphere or vacuum to a temperature of about
975.degree.C to about 1150.degree.C for a sufficient length of time
to decompose and volitilize the polytetrafluoroethylene binder, and
to flow the ASTM BNi-1 material so as to metallurgically wet the
tungsten carbide and the surface of the substrate. The substrate 11
and the coating (not shown) are cooled in a reducing atmosphere.
The resultant coating of tungsten carbide particles in a nickel
based alloy matrix is continuous, substantially uniform in
thickness and metallurgically bonded to the surface of the plain
carbon steel substrate.
A bond between a coating including tungsten carbide and a nickel
based alloy may have a shear strength up to 38,000 psi or
greater.
The wear resistant material content in the coating may be varied
from 0 to about 70 wt.%. The wear resistant material is
substantially uniformly distributed in the matrix material. Both
the particle size of the wear resistant and the material to be used
as a matrix as well as the wt.% of each can be varied to provide
coatings with controlled variations in hardness, wear resistance
and toughness. The coatings applied to substrate 11 may be applied
in thicknesses of from about 0.005 to about 0.06 inch with a
porosity less than about 5%.
Coatings of wear resistant material can be applied to substrates of
plain carbon steel, alloy steel, stainless steel, tool steel,
aerospace alloys, nickel based alloys, high density powder compacts
and the like.
This invention has numerous practical applications. These include,
but are not limited to, rolls including printing rolls, cutting
tools, collets, gripper jaws, threads, scribes, gears and the
like.
As disclosed hereinbefore, the stresses created in the flexible
self-supporting means by conforming it to the irregular surface
contour of the substrate are relieved by heating the
self-supporting means either subsequent to, simultaneous with or
prior to said conforming step. It is presently preferred to heat
the flexible self-supporting means during conforming it to the
substrate.
The foregoing detailed description has been given for clarity of
understanding only and no unnecessary limitations are to be
understood therefrom. The invention is not limited to the specific
embodiments shown and described for obvious modifications will
occur to those skilled in the art.
* * * * *