U.S. patent number RE29,815 [Application Number 05/806,924] was granted by the patent office on 1978-10-24 for cladding.
This patent grant is currently assigned to Avco Everett Research Laboratory, Inc.. Invention is credited to Daniel S. Gnanamuthu.
United States Patent |
RE29,815 |
Gnanamuthu |
October 24, 1978 |
Cladding
Abstract
A metal layer is clad to a metal substrate by laying spaced rods
or wires of a cladding metal on the substrate surface and scanning
the cladding metal with a continuously operating laser beam, part
of which impinges directly on the cladding metal to melt it and
part of which impinges on the adjacent surface area of the
substrate to improve flow of molten metal thereon. The cladding
metal may be fed to the substrate surface in synchronism with laser
beam scanning. The process produces a clad layer of the cladding
metal on the substrate characterized by a fine and homogeneous
structure within the clad on layer and further characterized by
uniform and high hardness compared to prior art cladding methods.
The surface of the clad may be smoothed by locally oscillating the
laser beam during the course of cladding and/or by multiple
passes.
Inventors: |
Gnanamuthu; Daniel S.
(Weymouth, MA) |
Assignee: |
Avco Everett Research Laboratory,
Inc. (Everett, MA)
|
Family
ID: |
24109675 |
Appl.
No.: |
05/806,924 |
Filed: |
June 15, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
529379 |
Dec 4, 1974 |
03952180 |
Apr 20, 1976 |
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Current U.S.
Class: |
219/121.64;
219/121.8; 219/76.1; 219/121.82 |
Current CPC
Class: |
B23K
26/34 (20130101); B23K 26/32 (20130101); B23K
2103/50 (20180801) |
Current International
Class: |
B23K
26/00 (20060101); B23K 26/34 (20060101); B23K
027/00 () |
Field of
Search: |
;219/76,121L,121LM,121BM,121EB,137 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,295,960 |
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Mar 1969 |
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DE |
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2,059,732 |
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Jan 1971 |
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FR |
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Primary Examiner: Truhe; J. V.
Assistant Examiner: Bell; Fred E.
Attorney, Agent or Firm: Frederick; M. E. Cohen; Jerry
Hieken; Charles
Claims
What is claimed:
1. Cladding method comprising,
continuously scanning a metal substrate surface with a CW operating
laser beam having a core power density of .Badd..[.29.]..Baddend.
.Iadd.20 .Iaddend.to 500 kilowatts per square inch in linear traces
with a longitudinal scanning speed along such linear trace of 5-50
inches per minute.
the scanning being carried out in a pattern to incrementally trace
the surface with spaced scan line patterns,
simultaneously feeding a cladding metal to the substrate surface to
intercept essentially the entire laser beam core and absorb
essentially the entire beam energy so that the cladding material is
melted and superheated and with application of laser beam power
thereto for an essentially continuous period of at least 100
milliseconds and so that the adjacent substrate surface is heat
treated at the same time to improve its wettability but melted only
to the extent of a superficial surface layer thereof.
2. Cladding method in accordance with claim 1 wherein the cladding
material is fed in elongated form having a width dimension
perpendicular to the scan line direction with a spacing of at least
one-half said width dimension between the loci of material feed
along adjacent spaced scan lines.
3. Cladding method in accordance with claim 1 and further
comprising,
locally oscillating the laser beam while scanning.
4. Cladding method in accordance with claim 1 and further
comprising,
rescanning the clad surface with a laser beam to smooth the
clad.
5. Cladding method in accordance with claim 4 wherein the laser
beam used for rescanning is maintained at 20 to 50 per cent of
power density of the original beam used for cladding.
6. Cladding method comprising,
butting elongated spaced units of cladding material against the
surface of a substrate of higher melting point than the cladding
material,
the average spacing between units being at least one-half of
average unit width,
impinging a beam of radiant energy from a CW laser upon the
cladding material units to heat said units and adjacent surface
areas of the substrate,
relatively scanning the beam longitudinally along said units of
cladding material and controlling heat input to melt and superheat
the units of cladding material while simultaneously heating the
adjacent substrate surface areas to enhance the flow of molten
cladding material thereon,
and wherein the laser beam is focused to a 0.025 to 1.0 inch
diameter circle, or area equivalent of other form, scans along the
cladding units at a rate 5 to 50 inches per minute and comprises a
power of 1 to 20 kilowatts.
7. Cladding method in accordance with claim 6 wherein the cladding
material units comprise rod or wire form.
8. Cladding method in accordance with claim 6 wherein the laser
beam is locally oscillated while scanning.
9. Cladding method in accordance with claim 6 wherein the laser
beam has a high power density core portion of less lateral width
than said units and an outer low power density fringe which
impinges directly on the space between units.
10. Cladding method in accordance with claim 6 wherein the laser
beam is of essentially the same width as the width of said units
and has a substantially uniform power density.
11. Cladding method in accordance with claim 6 wherein temperature
of the cladding material is controlled after superheating to cool
said material from superheat temperature to its melting (freezing)
point at a first rapid rate to maintain fine grain structure
therein,
and is thereafter cooled more slowly down to below about
1000.degree. F at a second slower rate to avoid cracking.
12. Cladding method in accordance with claim 11 wherein said first
rate is above 1000.degree. F per minute and said second rate is
below 1000.degree. F per minute.
13. Cladding method in accordance with claim 6 and further
comprising,
treating a surface layer of the substrate to lower its melting
point while cladding so that a thin skin portion of said surface
layer melts under cladding conditions.
14. Cladding method in accordance with claim 6 and further
comprising,
rescanning said radiant energy beam across the clad parts in at
least one additional scan after cladding to smooth the clad
surface.
15. Cladding method in accordance with claim 14 wherein said
additional scanning passes are made at lower power density than
used for cladding.
16. Cladding method in accordance with claim 6 and further
comprising,
providing temporal as well as physical spacing of the arrangement
of said spaced units.
17. Cladding method in accordance with claim 16 wherein
a length of cladding material is continuously fed into a radiant
energy beam through relative movement thereof while providing
relative movement between a substrate and the meeting point of the
beam and material,
said point being between the surface of said substrate and the
source of radiant energy beam.
Description
BACKGROUND OF THE INVENTION
The present invention relates to cladding metals upon metallic
substrates.
There are many known and long practiced methods for improving the
resistance of fabricated or semifabricated metal (including
elements, alloys and compounds) to wear, galling, spalling,
deformation, corrosion, heating and/or erosion. These include
overcoating the surface of the metal and modification of the
composition and/or microstructure of the surface through such
techniques as carburizing, nitriding, siliconizing, diffusion
hardening, hard surfacing (welding a high-alloy layer to the
surface), flame hardening, induction hardening and physical
modification (e.g. peening). The overcoating methods include
electroplating chromium or nickel onto the surface and roll
cladding (for sheet form or wire form mill products). Surfaces may
also be enhanced by cladding on materials through melting at the
substrate surfaces, such as by laying rods of hard material on the
metallic surface and melting by passing the flame of an
oxy-acetylene torch thereover. Surfaces may also be enhanced by
forming alloys in situ through deposition of minor alloy components
and heating with a laser to produce melting and diffusion as taught
in the co-pending application of Gnanamuthu, et al., Ser. No.
431,240, filed Jan. 7, 1974.
It is an important object of the present invention to provide a
cladding method effective to produce high adherence of a thick
layer of metal to the surface of a substrate.
It is a further object of the invention to provide fine and
homogeneous microstructure within the clad-on layer consistent with
the preceding object.
It is a further object of the invention to provide high and uniform
hardness within the clad-on layer consistent with one or more of
the proceeding objects.
It is a further object of the invention to minimize interdiffusion
between cladding and substrate materials consistent with one or
more of the preceding objects.
It is a further object of the invention to provide a smooth clad
surface consistent with one or more of the preceding objects.
It is a further object of the invention to provide high density -
low porosity surface layers of materials consistent with one or
more of the preceding objects.
It is a further object of the invention to utilize standard
equipments borrowed from other major purposes and not necessarily
dedicated to surface modification consistent with one or more of
the preceding objects.
It is a further object of the invention to provide flexibility of
process control consistent with one or more of the preceding
objects.
It is a further object of the invention to minimize incidental
effects on the substrate below the surface layer consistent with
one or more of the preceding objects.
It is a further object of the invention to provide minimal working
time and related substrate preparation and posttreatment times
consistent with one or more of the preceding objects.
SUMMARY OF THE INVENTION
In accordance with the invention, one or more units of cladding
material are placed face to face with a substrate surface to be
clad and a continuous wave output (cw) laser beam, is scanned along
the cladding material to melt it. The units are of elongated form,
i.e., rod, wire or ribbon and the scanning is carried out
longitudinally, i.e., parallel to the direction of elongation. The
rate of scanning is such that the melted material resolidifies very
quickly as a bonded on clad at the substrate surface. During the
brief time of residence in the molten state, the molten material
flows laterally along the substrate surface.
A laser beam core portion containing a majority of the radiant
energy of the beam impacts the cladding material for melting and a
fringe portion of the beam impacts the adjacent substrate surface
area to make it more readily wettable by the molten cladding
material and allow more uniform flow. The relative motion between
the substrate and laser beam for scanning may be effected by beam
deflection, substrate movement or a combination of the two.
Multiple spaced units of cladding material may be placed on the
substrate surface at the same time or in a sequence, synchronized
with a scanning rate. The resultant clad on layer often has a wavy
form with peaks at the sites of cladding material placement. If it
is desired to avoid the wavy surface of resultant clad material,
then the clad on layer can be smoothed by locally oscillating the
radiant energy beam during cladding and/or through multiple heating
passes. The spacing between units of cladding material is
preferably at least one-half of unit width.
It has been found in the practice of the invention that massive
reinforcing particles of high hardness in the cladding material
such as carbide particles in stellite alloy rods are dissolved in
the melting cladding material and upon resolidification are
reproduced in the matrix at a much finer scale than they originally
appeared in the rods, thereby giving the clad on layer in a high
uniform hardness. This is in contrast to microstructures observed
in such conventional processes as oxy-acetylene cladding wherein
large inclusions of carbide particles may be observed in the
finished clad. Starting composition of the cladding material is
preserved in the final product of the present invention; there is
very low interdiffusion with or dilution by substrate material.
The radiant energy beam size for purposes of the present invention
is from 0.025 inch to 1.0 inch diameter circle, or non-circular
forms of the equivalent area, applied with a power of 1 to 20
kilowatts at a scanning rate of 5 to 50 inches per minute. Among
the cladding materials which may be advantageously applied through
use of the present invention are cobalt, iron and/or nickel base
alloys and other alloys or pure metals or intermatallic compounds.
The suitable substrates include essentially all metallic elements,
compounds and alloys. However, the substrate material must not melt
(excepting optionally, for a thin surface layer thereof as
described below) under conditions of melting and superheating the
cladding material.
These and other objects, features and advantages of the invention
will be apparent from the following detailed description of
preferred embodiments of the invention taken in conjunction with
the accompanying drawing in which:
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an isometric, partly sectioned sketch of a substrate
metallic plate being clad in accordance with a preferred embodiment
of the process of the invention and indicating the scanning radiant
energy beam which does the cladding;
FIG. 1A is a temperature-time profile for cooling the plate in the
above process;
FIGS. 2 and 2A are cross-sectional views of FIG. 1 materials after
single and multiple cladding passes;
FIGS. 3 and 4 are isometric partly sectioned sketches of substrates
being clad in accordance with further preferred embodiments of the
invention, and;
FIG. 5 is a graph showing hardness profile of the clad and
underlying substrate after treatment in accordance with a preferred
embodiment of the invention;
FIG. 6 is a similar profile of alloying elements;
FIG. 7-10 are photomicrographs of clads made, respectively, in
accordance with the prior art and the processes of the above
described three embodiments of the present invention;
FIG. 11 is a drawing of a photomicrograph of a clad made in
accordance with the processes of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown a substrate plate 10 in the
course of cladding in accordance with a preferred embodiment of the
present invention. For purposes of this illustration, it is
indicated that three rods of cladding material have been applied
and one of them, 12, has already been method, another, 14, is in
the course of melting and a third, 16, has not yet been melted. The
heat affected zone of the substrate underlying the first melted rod
12 is indicated at 18. The melting is carried out by laser beam 20
having a core portion 22 and a fringe portion 24 of the beam. The
scanning is carried back and forth lengthwise along the rods with
the loci of beam impact in successive scanning passes overlapping
so that there will be a continuous heat affected zone running along
the surface 11 of the substrate.
Before cladding, surface 11 may be coated with a 1/4- 1/2 mil thick
layer of manganese phosphate using any of several known commercial
phosphating processes or coating by application of a slurry of
graphite in isopropyl alcohol and heating to drive off the alcohol
to improve the radiant energy absorbtivity of the surface. Carbon
black may also be applied as the absorbing coating. The rods are
not coated. Also, before cladding, it is preferable to preheat the
substrate 10, typically to about 400.degree.-700.degree. C, and
then apply the cladding material. The cladding material may be in
forms other than rod forms as indicated in the drawings, such as
strips or spheres for instance. However, there should be spaces of
exposed substrate surface between units of cladding material to
allow the flow of molten cladding material.
The clad parts are preferably post heated to avoid formation of
cracks caused by rapid cooling. FIG. 1A shows a typical profile for
temperature vs. time in cooling, indicating a very rapid cooling
from superheat temperature to melting point [A to B] to produce
fine grain structure in the clad on part. Slow cooling down to C
(about 800.degree. F) prevents cracking and rapid cooling may be
thereafter maintained down to room temperature.
During laser scanning, an inert, reducing or carburizing atmosphere
may be employed. Use of a carburizing atmosphere is preferred on
iron or steel parts to lower the melting point of a limited surface
portion of the substrate to enhance flow of the molten cladding
material thereon.
For a typical case, stellite rods are melted at approximately
2400.degree. F and superheated to approximately 3000.degree. F,
cooled in half a second back to 2400.degree. at 1200.degree. F/sec.
(A to B), then cooled for 15 minutes at 107.degree. F/min. The
substrate (e.g., steel) stays below its melting point at
2700.degree.-2800.degree. F. But a surface layer thereof may be
carburized in a suitable carburizing atmosphere, e.g., using an
oxy-acetylene torch so that its melting point will be about
2600.degree. F and this temperature is reached during cladding.
The core of the beam is preferably limited to a size smaller than
the diameter of width of the cladding rod to avoid direct
impingement on the substrate space between rods. The rods absorb
sufficient laser power that melting heat input to the substrate is
avoided excepting in said limited surface portion thereof. To this
end thick units of cladding material of at least 10 mils and
preferably on the order of 50-200 mils are continuously arrayed in
the path of the high power density beam.
FIG. 2 shows the resultant clad product produced in accordance with
processing of FIG. 1 wherein the three melted rods 12, 14, and 16
are resolidified as a continuous clad of wavy profile. This
waviness may be avoided by locally oscillating the laser beam in
the course of melting; that is, by laterally or longitudinally
oscillating the beam at a rate much higher than its scanning rate.
Multiple passes, preferably with local oscillation, also tend to
produce the greatest smoothness of the clad. Such smoothing
techniques may be utilized to avoid the need for expensive surface
grinding of the clad after completion of the process. The resultant
smoothed clad product is indicated in FIG. 2A wherein the
clad-on-layer is indicated at 17.
Preferably, a 2-20 kilowatt laser beam focused to a 0.025 to 0.7
inches diameter circle or area equivalent of other form with a core
diameter of 1/8-1/2 total beam diameter, is scanned across the
surface to be clad at a rate of 5 to 25 inches per minute. Power
density of the core of the beam for cladding .[.at the focal point
can be considered to possess a.]. .Iadd.is .Iaddend.20 to 500
kw/in.sup.2. The beam energy distribution .Iadd.at the focal point
can be considered to possess a .Iaddend..[.is.]. Gaussian
.Iadd.distribution .Iaddend.and defines concentric Airy discs with
the core disc being typically 1/8(0.025) inches and having a power
density of 34.2 kw/cm.sup.2, the density averaged over the second
Airy disc (1/4 inch diameter) being 13.4 kw/cm.sup.2 for 10 kw of
total laser power.
In local oscillation, the rate of oscillating is such, in relation
to scan rate, that the beam core impinges the same point at least
500, preferably at least 1000, times during the said period of
molten state residence. For instance, during a 9 inch per minute
scan by a 1/4 inch beam (calculated on second Airy disc) locally
oscillated at 690 Hertz, over half an inch of lateral travel, the
beam will impinge the same point 1150 times. The total energy
applied is typically 1000-5000 Joules over a period of 100 or more
milliseconds thereby allowing time for melting, superheating and
smoothening flow of the cladding material.
The scan pattern is in linear traces of adjacent closely spaced
parallel lines which work incrementally across an area to be clad
Local oscillation, it used, may be longitudinal (i.e., parallel to
scan line direction). Lateral (orthogonal to scan) or a combination
of the two and/or may comprise beam cross-section-form changing
such as a change from circular to cruciform or stellate.
The power destiny used for smoothening the successive clad zones is
20 to 50 percent of that for cladding. Typical times of residence
in the molten state for any given portion of cladding material are
0.1 to 2.0 seconds. It is also possible to produce a laser beam
without a high power density core relative to a low power density
fringe, i.e., having substantially uniform power density, and such
a beam may be essentially as wide as the diameter of the rods to be
melted thereby. Heat transfer to the substrate via the cladding
material provides the necessary substrate surface conditioning
improving its wettability but limiting substrate melting to a
superficial surface layer thereof, i.e., less than 1/5 of clad
thickness.
It is important to control heating conditions so that the cladding
material not only melts, but is superheated so that the lowest
melting phase dissolves other phases thereof. In the case of
stellite rods, this superheating allows massive carbide particle
inclusions to be dissolved. The rapid rate of scanning allows quick
cooling and prevents the regrowth of precipitates.
High power lasers suitable for use in connection with the present
invention may be the type shown in the copending application of
Edward V. Locke and Richard A. Hella, Ser. No. 322,783, filed Jan.
11, 1973, now U.S. Pat. No. 3,817,606 of common assignment with the
present application and in U.S. Pat. No. 3,702,973 granted Nov. 14,
1972, the disclosures of which are incorporated herein by reference
as though set out at length herein. Such lasers comprise an
exciting electron beam source chamber and a gas lasing chamber with
a lasing gas (e.g., a mixture of helium, nitrogen and carbon
dioxide) and an optical cavity. The electron beam initiates and
sustains lasing activity within the optical cavity and an output
light beam is controlled by deflection optics and beam tunnels to
scan, and cut off (if necessary) the light beam.
FIG. 3 and 4 show further preferred embodiments of the invention in
which spaced units of cladding material are melted and resolidified
to form a continuous clad-on layer on the surface of a substrate.
Both embodiments are illustrated with respect to a substrate plate
32 mounted on a work table 34 which traverses in working passes, in
a direction indicated by arrow 36, under a laser 38 which emits a
beam 40. The table makes incremental lateral steps by movement in
the direction indicated by arrow 42 at the end of each working pass
and retraces by movement in the direction indicated by arrow 44.
The laser beam may be shut off (deflected) during retrace or
applied during retrace as desired.
In both FIGS. 3 and 4, two rows 46 of clad have been formed and a
third row 48 is partially completed. In the remaining unworked area
50 of the substrate surface the spaced units of cladding material
comprise a layer of spaced powder particles 52 in FIG. 3 and, in
FIG. 4, a wire 54 fed continuously by a feeder 56 to a point under
the beam 40 in contact with the substrate surface. The wire is fed
in sequence along adjacent parallel paths, spaced from each other
by a distance of one-half to one wire diameter.
In the FIG. 3 embodiment, the porosity of the loose powder provides
the necessary spacing between units for flow of molten material and
to limit the molten zone to a predetermined strip region related to
laser beam width.
In the FIG. 4 embodiment, the wire feeding, together with the
described workpiece displacement provides temporal as well as
physical spacing between units of cladding material.
In all the embodiments of the invention the laser and/or its beam
may be moved in lieu of, or in addition to, workpiece displacement
to effect scanning. Multiple laser beams may be employed for the
functions of melting and superheating the cladding material and
heating adjacent substrate surface area to enhance the wettability
of substrate surface to allow flow of molten cladding material
thereon. The spacing between units of cladding material on the
substrate surface initially applied should be at least one-half the
average span on the substrate surface of the units surrounding each
space and no greater than a distance which would lead to
discontinuity between adjacent melted and resolidified units.
Preferably, spacings and cladding units sizes will be in the same
dimensional range, e.g., parallel 1/8-1/4 inch rods of cladding
material spaced 1/8-1/4 inch apart (on a rod center-to-rod center
basis). In the extreme case, circular cross-section rods may be
placed side-by-side allowing the exposed substrate surface under
their lower curves to constitute the flow distance.
The practice of the invention is further illustrated by the
following non-limiting examples. All of the values given for laser
beam power and power density given in the following examples are
given for that calculated to be at the surface of the
workpiece.
EXAMPLE 1
A substrate plate of AISI 4815 steel was coated with a 1/4 mil
thick layer of manganese phosphate and then preheated to about
450.degree. to 500.degree. F in a furnace. Then the plate was
removed from the furnace and stellite rods of 1/8 inch diameter
(Stellite Alloy No. 1, cast) were placed on the plate with a
spacing of 1/4 inch between rods. An unoscillated laser beam of
approximately 1/8 inch in core diameter and 3 kilowatts power was
scanned along the length of the rods, back and forth at a scanning
rate of 10 inches per minute. A mixture of argon flowing at 5 cubic
feet per hour and hydrogen flowing at 10 cubic feet per hour were
used as a shielding gas. The stellite rods melted and flowed over
the steel plate and resolidified as a well bonded clad. The laser
core power density was 66 kw/in.sup.2.
FIG. 5 shows hardness of the clad zone as a function of case depth
of the clad-on layer. The clad zone is 0.05 inch thick and in this
zone hardness is between 58 and 63 on a Rockwell C scale while the
hardness of the heat affected zone underlying the clad and of the
base metal of the substrate is less than 30 on the same Rockwell C
scale. FIG. 6 shows chemical composition of the clad zone as a
function of depth of the clad wherein it is seen that the
concentration of the stellite ingredients, cobalt, chromium, and
tungsten, is essentially constant with depth and in amounts
corresponding essentially to that of the original stellite rods,
thus indicating that during laser cladding there is very little
dilution of the cladding material with substrate material.
FIGS. 7 and 8 are microstructures of clads made in accordance with
oxy-acetylene cladding and laser cladding, respectively. The
oxy-acetylene clad shows massive carbide particles of high hardness
(Rockwell C70 or more) embedded in a soft matrix (Rockwell C45) and
displays on overall hardness of Rockwell C51. On the other hand,
the laser clad shows a homogeneous and a fine microstructure of
uniform hardness of Rockwell C60.
EXAMPLE 2
The same substrate and cladding materials as in Example I were
processed through a second pass (after preheating at 900.degree. F)
using local oscillation of the laser beam which was scanned at a
rate of 10 inches per minute with 5.25 kw power. Local oscillation
was performed at 690 Hertz in a direction perpendicular to
scanning. The basic laser beam size was a rectangle of 1/8 inch
long by 1/2 inch wide (the length dimension being parallel to the
scanning direction and the width dimension being orthogonal
thereto) and the scanning achieved an effective laser beam width of
1/2 in. The laser processing was carried out in an atmosphere
formed by argon flowing through at 5 cubic feet per hour and
hydrogen at 10 cubic feet per hour. The clad substrate was
postheated at 900.degree. F for 5 minutes. The result was that the
clad surface was made essentially flat in contrast to a wavy
surface in the product of Example I. The average hardness of the
clad layer was 55 and that of the substrate was 20 (both on
Rockwell C scale.) The laser core power density was 23
kw/in.sup.2.
EXAMPLE III
Cast Stellite Alloy No. 1 rods of 3/16 inch diameter spaced 3/16
inch apart were clad on AISI 4340 plate substrates, preheated to
900.degree. F, by using a laser beam with a scanning speed of 10
inches/minute in an oxygen, acetylene gas mixture atmosphere under
carburizing conditions. The laser beam power was 12.75 kw. The core
power density was 280 kw/in.sup.2. The clad substrate was post
heated with oxy-acetylene flame for 3 minutes. The clad-on layer
had an average hardness of 60 (Rockwell C). The base metal hardness
was 36 (Rockwell C).
EXAMPLE IV
Rods of 3/16 inch diameter cast Stellite Alloy No. 6 were clad on
AISI 4815 plate substrate preheated to 700.degree. F, in oxygen,
acetylene gas mixture under carburizing conditions. The laser
scanning speed was 10 inches per minute and laser power was 9 kw.
The core power density was 198 kw/in.sup.2. The clad substrate was
post heated with oxy-acetylene flame for 1 minute. The resultant
clad on layer had an average hardness of 48 (Rockwell C) and the
average base metal hardness was 20 (Rockwell C).
EXAMPLE V
Dura-Face .[.alloys.]. .Iadd.alloy, a powderlike coating layer of
.Iaddend.an alloy containing nickel, chromium, and silicates,
manufactured by Ingersoll Products Division of Borg Warner
Corporation, .Iadd.and applied on substrates by plasma or flame
spray .Iaddend.was clad onto AISI C1080 plate substrates .Iadd.by
laser scanning. .Iaddend.No preheating or post heating was used
.Iadd.except as incidental to the Dura-Face application before
laser treatment. .Iaddend.The working atmosphere comprised of argon
flowing at 5 cubic feet per hour and hydrogen flowing at 5 cubic
feet per hour. The scanning speed was 10 inches/minute. The
thickness of applied cladding material was 0.080 inch. The width of
applied cladding material was 1 inch. The laser power was 10.5 kw.
The beam size was 1/2 inch wide by 1/8 inch long as that used in
Example II. The core power density was 47 kw/in.sup.2. The average
hardness of the clad-on layer was 64 (Rockwell C) and the average
base metal hardness was 20 (Rockwell C).
EXAMPLE VI
AISI 304 stainless steel was clad on AISI C1018 plate substrates.
The scanning speed was 8 inches per minute. No preheating or post
heating was used. The laser power was 13.5 kw. The effective beam
size was 3/8 inch wide by 1/8 inch long. The core power density was
80 kw/in.sup.2. Hydrogen flowing at 10 cubic feet per hour formed
the working atmosphere. The thickness of cladding material was
0.040 inch and the width of the cladding material was 3/8 inches.
The average hardness of the clad-on layer was 88 (Rockwell B) and
the base metal hardness was 88 (Rockwell B). A cross-sectional view
of the cladding is indicated in FIG. 9.
EXAMPLE VII
Nickel powder was spread on AISIC 1018 substrate plates and clad
thereon by scanning at 20 in/min. The nickel powder was -325 mesh
size (U.S. standard corresponding to zero to 44 micron diameter
spheres) and sprinkled on a substrate surface precoated with 1/4
mil thick manganese .[.phosphates.]. .Iadd.phosphate.Iaddend..
Thickness of the powder sprinkled was 0.005 inch. The working
atmosphere was hydrogen flowing at 5 cubic feet per hour. No
preheating or post heating was used. Laser power was 9 kw and
effective beam size was 1/8 inch long by 1/2 inch wide. The core
power density was 40 kw/in.sup.2. A cross-section photomicrograph
of the resultant product is shown in FIG. 10.
FIG. 11 is a drawing of a photomicrograph at five times
magnification of a sawed and polished cross-section of a layer 12
clad to an AISI 4815 steel substrate in accordance with Examples I
and corresponding essentially to the schematic illustration of a
similar product in FIG. 2. The heat affected zone 18 is bounded by
an internal band 19 which is clearly recognizable at this level of
magnification.
It is evident that those skilled in the art, once given the benefit
of the foregoing disclosure, may now make numerous other uses and
modificatons of, and departures from the specific embodiments
described herein without departing from the inventive concepts.
Consequently, the invention is to be construed as embracing each
and every novel feature and novel combination of features present
in, or possessed by the apparatus and techniques herein disclosed
and limited solely by the scope and spirit of the appended
claims.
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