U.S. patent application number 14/785134 was filed with the patent office on 2016-03-24 for laser assisted interstitial alloying for improved wear resistance.
The applicant listed for this patent is DM3D TECHNOLOGY, LLC. Invention is credited to Bhaskar DUTTA.
Application Number | 20160083850 14/785134 |
Document ID | / |
Family ID | 51731819 |
Filed Date | 2016-03-24 |
United States Patent
Application |
20160083850 |
Kind Code |
A1 |
DUTTA; Bhaskar |
March 24, 2016 |
LASER ASSISTED INTERSTITIAL ALLOYING FOR IMPROVED WEAR
RESISTANCE
Abstract
A method of enhancing wear resistance of a metallic substrate
includes applying a coating of an interstitial element to a surface
of a substrate. A laser beam is directed onto a localized area of
the metallic substrate coated with the interstitial element locally
raising a temperature of the metallic substrate to a temperature
causing the interstitial element to diffuse into the substrate. A
layer of alloy including the interstitial element is generated onto
the localized area of the metallic substrate. A focal point of the
laser beam is disposed at a location spaced from the surface of the
substrate for optimizing a power density of the laser beam at the
surface of the substrate. The coating of interstitial element not
diffused into the substrate is removed exposing the layer of alloy
including the interstitial element.
Inventors: |
DUTTA; Bhaskar; (Troy,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DM3D TECHNOLOGY, LLC |
Auburn Hills |
MI |
US |
|
|
Family ID: |
51731819 |
Appl. No.: |
14/785134 |
Filed: |
April 16, 2014 |
PCT Filed: |
April 16, 2014 |
PCT NO: |
PCT/US14/34334 |
371 Date: |
October 16, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61813297 |
Apr 18, 2013 |
|
|
|
Current U.S.
Class: |
427/554 |
Current CPC
Class: |
C23C 24/082 20130101;
C21D 1/72 20130101; C21D 1/68 20130101; C21D 1/09 20130101; C23C
8/00 20130101; C23C 24/04 20130101 |
International
Class: |
C23C 24/08 20060101
C23C024/08; C21D 1/09 20060101 C21D001/09 |
Claims
1. A method of enhancing wear resistance of a metallic substrate,
comprising the steps of: providing a metallic substrate; applying a
coating including an interstitial element to a surface of the
substrate; directing a laser beam onto a localized area of the
metallic substrate coated with the interstitial element thereby
locally raising a temperature of the metallic substrate to a
temperature causing the interstitial element to diffuse into the
substrate providing a layer of alloy including the interstitial
element onto the localized area of the metallic substrate;
positioning a focal point of the laser beam at a location spaced
from the surface of the substrate for optimizing a power density of
the laser beam at the surface of the substrate; and removing the
coating of interstitial element not diffused into the substrate
thereby exposing the layer of alloy including the interstitial
element.
2. The method set forth in claim 1, wherein said step of directing
the laser beam is further defined by directing the laser beam along
a three dimensional surface of the metallic substrate.
3. The method set forth in claim 2, wherein said step of directing
the laser beam along a three dimensional surface of the metallic
substrate is further defined by directing said laser beam with
computer data defining a configuration of said metallic
substrate.
4. The method set forth in claim 1, wherein said step of applying a
coating of an interstitial element is further defined by providing
a coating comprising at least one of hydrogen, boron, carbon,
nitrogen, or combinations thereof.
5. The method set forth in claim 1, wherein said step of providing
a metallic substrate is further defined by providing iron-alloys
(steel), nickel-alloys, cobalt-alloys, aluminum-alloys, and
copper-alloys.
6. The method set forth in claim 1, wherein said step of providing
a metallic substrate is further defined by providing a metallic
substrate with a surface roughness having an Ra value less than
about 50 microns and an Rt less than about 100 microns.
7. The method set forth in claim 1, wherein said step of causing
the interstitial element to diffuse into the substrate providing a
layer of alloy including the interstitial element is further
defined by causing the interstitial element to diffuse into the
substrate to a depth of between 30 microns and 500 microns.
8. The method set forth in claim 7, further including controlling
the depth of diffusion of the interstitial element by adjusting
power density and laser traverse speed of the laser beam.
9. The method set forth in claim 1, wherein said step of applying a
coating of an interstitial element to the substrate is further
defined by applying a powdered interstitial element using an
aerosol spray or applying a tape of comprising the interstitial
element to a predetermined location.
10. The method set forth in claim 1, wherein directing a laser beam
onto a localized area of the metallic substrate is further defined
by adjusting a shape of the laser beam projected onto the localize
area of the metallic substrate.
11. The method set forth in claim 1, wherein said step of directing
a laser beam onto a localized area of the metallic substrate is
further defined by providing a laser beam comprising a CO.sub.2
laser, a diode laser, a fiber optic laser delivering a laser beam
directly to the surface of the substrate, and equivalents
thereof.
12. The method set forth in claim 1, further including the step of
heating the metallic substrate during or prior to applying the
coating of interstitial element for vaporizing solvent disposed in
the coating of the interstitial element.
13. The method set forth in claim 1, wherein said step of applying
a coating of interstitial element is further defined by applying a
coating including the interstitial element comprising a volatile
solvent capable of evaporating from the coating including the
interstitial element while the substrate is disposed at ambient
temperature.
14. The method set forth in claim 1, wherein said step of directing
a laser beam onto a localized area of the metallic substrate is
further defined by directing a divergent laser beam onto the
metallic substrate.
Description
PRIOR APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 61/813,297, filed Apr. 18, 2013.
TECHNICAL FIELD
[0002] The present application relates generally toward an improved
process for increasing hardness of a soft metallic substrate. More
specifically, the present invention relates toward the use of a
laser to assist interstitial alloying of a soft metallic
substrate.
BACKGROUND
[0003] A dichotomy exists when selecting metallic substrate for use
in industrial processes or mechanical devices that are subject to
frictional forces. During a fabricating or forming process, it is
preferable to select a soft material for ease of forming. However,
a selection of soft material substrates results in poor durability,
particularly when the device is subject to frictional forces.
Therefore, when durability of a mechanical device is desired, a
hard metallic substrate is selected, which is problematic when
fabricating or forming the device.
[0004] Various attempts have been made to coat soft metallic
substrates to improve wear resistance and related material loss
known to cause adverse dimensional changes to the substrate. For
example, plasma coatings and weld overlays have been used, but
offer limited durability and significantly increase the cost of
fabricating due to requisite post-machining operations. Vapor
deposition has also been used to increase surface hardness.
However, mechanical bonds between the coating and the substrate are
weak causing the coating to degrade or lose adhesion causing vapor
deposition to be of limited use.
[0005] Diffusion of interstitial elements having higher a hardness
value than a soft alloy substrate has been experimented with, but
has not achieved significant industrial use. Various attempts to
improve control over an interstitial alloying have not proven
affective. Therefore, it would be desirable to provide an enhanced
process for increasing a hardness of a substrate by way of
diffusion of an interstitial alloy.
SUMMARY
[0006] A method of enhancing wear resistance of a metallic
substrate includes applying a coating including an interstitial
element to a surface of the substrate. A laser beam is directed
onto a localized area of the metallic substrate coated with the
interstitial element. The laser beam locally raises a temperature
of the metallic substrate to a temperature causing the interstitial
element to diffuse into the substrate providing a layer of alloy
including the interstitial element onto the localized area of the
metallic substrate. A focal point of a laser beam is positioned at
a spaced location from the surface of the substrate to optimize a
power density of the laser beam at the surface of the substrate.
The coating of the interstitial element not diffused into the
substrate is removed exposing a layer of alloy including the
interstitial element.
[0007] The present inventive method provides an enhanced ability to
control excitation of substrate molecules to control diffusion of
interstitial elements into a soft metallic substrate. By
controlling the focal point relative to the surface of the
substrate an optimum energy beam and energy configuration is
achieved to enhance control over the diffusion process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Other advantages of the present invention will be readily
appreciated, as the same becomes better understood by reference to
the following detail description when considered in connection with
the accompanying drawings, wherein:
[0009] FIG. 1 shows a metallic substrate;
[0010] FIG. 2 shows a metallic substrate with a localized
application of a coating including an interstitial element;
[0011] FIG. 3 shows a laser heating a localized area of the soft
metallic substrate having a coating including an interstitial
element;
[0012] FIG. 4 shows an alternative method of locally raising a
temperature of the soft metallic substrate;
[0013] FIG. 5 shows a cylindrical component being subject to the
method of the present invention;
[0014] FIG. 6 shows a process of diffusing an inside of a tubular
component using a galvanometer to redirect the laser beam of the
present application; and
[0015] FIG. 7 shows a chart of experimental hardness of a substrate
being subject to the method of the present invention.
DETAILED DESCRIPTION
[0016] Referring to FIG. 1, a metallic substrate in the form of a
planar component is generally shown at 10. The metallic substrate
10 is contemplated to be formed from metals, such as, for example,
various steels, nickel alloys, cobalt alloys, aluminum alloys, and
copper alloys. It is anticipated that the substrate 10 is machined
or formed into a final shape through grinding, machining, or
turning as is known to those of skill in the art. The substrate 10
is contemplated by the inventor to be any substrate 10 subject to
frictional or other mechanical forces known to degrade the geometry
and function of the substrate 10.
[0017] Knives, mechanical parts, such as, for example, piston
heads, other internal combustion elements and any metallic
component subject to wear are all believed to be enhanced by the
process of the present invention. After processing, the substrate
10, it is desirable to include a surface roughness having an Ra
value of less than about 20 microns and an Rt value of less than
about 100 microns. As set forth above, the part geometry includes a
flat knife blade, a rotary knife blade, an engine cylinder liner,
or a piston ring for an engine. It should be understood by those of
ordinary skill in the art that any metallic substrate subject to
durability requirements is included within the scope of this
invention.
[0018] FIG. 2 shows the metallic substrate 10 having a coating 12
applied over an area of interest known to be subject to frictional
forces. The coating includes an interstitial element having an
atomic size known to allow diffusion into a lattice structure of an
alloy. More specifically, the coating includes at least one of
hydrogen, boron, carbon, or nitrogen. Additionally, combinations of
these interstitial elements are included within the scope of this
invention to further enhance wear resistance of the metallic
substrate 10.
[0019] The coating 12 is applied either as a powder, or a liquid,
in which case, a solvent is used to liquefy and suspend the
interstitial element of choice. The solvent is either water or
organic, but is selected to flash from the surface of the substrate
10 without requiring significant amount of time or heat. When a
liquid coating 12 is applied to the substrate 10, the substrate 10
is preheated in an oven to a temperature of about 240.degree. C.
for about 20 minutes so that the substrate (or component) receives
a uniform temperature. It should be understood by those of ordinary
skill in the art that the temperature selected to flash the solvent
from the coating 12 is below the melting temperature of the
substrate 10 alloy to prevent adversely affecting the dimensional
configuration of the component. After preheating, the component is
removed from an oven and a coating including carbon black powder is
applied, or other interstitial element, using an aerosol or
atomizing spray method. The coating includes a uniform thickness
over the surface requiring improved wear resistance. In the
alternative, a tape comprising an interstitial element is applied
to an area of interest that requires enhanced wear protection.
[0020] Referring now to FIG. 3, a laser 14 is shown projecting a
laser beam 16 (or energy beam) onto an area of interest 18 that has
received a coating 12 including an interstitial element. The laser
comprises a CO.sub.2 laser, a diode laser, a fiber optic laser, or
any equivalent energy source, capable of directing the laser beam
16 to a localized area of interest 18 of the substrate. The laser
beam 16 defines a laser focal point 20 that is located at a
position spaced from the surface of the substrate 10 determined to
optimize the power density of the laser beam at the surface of the
substrate 10. For example, it is believed that locating the focal
point on the surface of the substrate 10 or too close to the
surface of a substrate results in generating a cast iron surface
known not to provide durable property achieved by proper diffusion
of an interstitial element. Therefore, the location of the focal
point 20 is predetermined to provide a proper amount of energy to
excite the lattice structure of the substrate alloy material known
to allow diffusion of the interstitial element to a proper
depth.
[0021] In one embodiment, the laser beam is a divergent laser beam
where the focal point 20 is spaced above the surface 22 of the
substrate 10. It is within the scope of the invention that the
laser beam is a convergent laser beam where the focal point 20
would be positioned below the surface 22 of the substrate 10.
[0022] The surface 22 of the substrate 10 does not melt under
optimum circumstances. The avoidance of a eutectic reaction which
would result in the interstitial element reacting with the
substrate 10 alloy is desirable. The optimum effect of the laser
(or energy) beam 16 on the substrate is to merely excite the
molecular lattice of the substrate 10 alloy. As such, an optimum
laser power and speed is predetermined for each application based
upon the substrate alloy and the desired depth of diffusion of the
interstitial element. In one embodiment, a CO.sub.2 laser provides
an adequate amount of energy to the substrate 10. In other
embodiments, a diode laser is preferable. Additionally, the laser
14 is modified to project an alternatively shaped laser beam 16
onto the area of interest of the substrate 10. In some application,
a rectangular shaped laser beam 16 is preferable, such as, for
example a 12.times.1 millimeter or 20.times.1 millimeter shape
laser beam. Further applications make use of a round spot of 2
millimeters or 4 millimeters diameter, or an oval shape. In this
regard, a shaping nozzle 36 (FIG. 6) is used.
[0023] In some applications, rapid diffusion of the interstitial
element into the substrate 10 required a serpentine path 24 be
established. This is best represented in FIG. 4 where the laser
beam zig zags to cover more surface area than capable by a single
pass across an area interest of the metallic substrate 10. An
optimum path of travel is determined based upon a level of energy
required to diffuse the interstitial element into the substrate 10,
which will dictate a size of the laser beam 16 at the surface 22 of
the substrate 10. It should be understood by those of ordinary
skill in the art that either the laser 14 or the substrate 10 is
movable so that the laser beam 16 provides an adequate amount of
excitation energy to the substrate 10.
[0024] FIG. 5 shows the ability of the present inventive method to
diffuse an interstitial element into components having various
three dimensional configurations. In this instance, a cylindrical
element, such as, for example, a piston rotates relative to the
laser beam 16 to provide a single circumferential band 24 around an
exterior surface 26 of the component. It is contemplated by the
inventor that either circular tool path or rectangular tool path
provides an adequate level of excitation energy to the substrate
10.
[0025] To further control diffusion of the interstitial element,
the laser 14 interfaces with a computer aided design (CAD) data to
adjust the location of the focal point of the laser beam 16 to
maintain a constant distance from the surface of a three
dimensional substrate 10. The CAD data is used to direct the laser
to either adjust a physical location relative to the substrate 10
or adjust the focal point 20 by way of a controller (not shown).
Alternatively, the substrate 10 is moved relative to the laser 14
by the controller.
[0026] A still further embodiment is shown at FIG. 6 where
interstitial diffusion into a substrate 10 is desired on an
interior surface 28 of a tubular component 30. In this embodiment,
a laser beam 32 is directed toward a galvanometer-controlled mirror
34 to redirect the laser beam 32. Once redirected, the laser beam
32 passes through a shaping nozzle 36 directing the divergent beam
38 onto an area of interest 40 on the inner surface 28 of the
tubular component 30.
[0027] Tests have shown that the diffusion of the interstitial
element ranges between a depth of 30 microns and 500 microns. The
table shown in FIG. 7 provides the test results where significant
hardness improvement is achieved up to 10 millimeters from an edge
of a knife blade (not shown). In this example, 1018 steel was
coated with carbon powder and subject to excitation by way of a
laser beam 16, 38 as explained above. Maximum hardness of around
900 VHS is achieved to 9 millimeters indicating the density of the
interstitial carbides similar or equal to the density of
interstitial carbides at the surface. Hardness requirements of a
given application are achieved by adjusting the strength and speed
of the laser treatment of the area of interest on the substrate 10.
The range of depth from the knife edge where hardness drops from
above 800 VHS to that of the un-alloyed substrate, or in this
example around 300 VHS is identified as the transition zone. At 11
millimeters the hardness drops that of the unalloyed substrate.
[0028] Following treatment of the component, the surface 22 of the
metallic substrate 10 is polished to remove interstitial element
not diffused into the substrate 10. In one embodiment, the surface
is cleaned and polished with a diamond paste having 0.3 micron
sized diamond particles mixed into a kerosene solution. However, it
should be understood by those of ordinary skill in the art that
alternative polishing methods will suffice.
[0029] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. The
foregoing invention has been described in accordance with the
relevant legal standards; thus, the description is exemplary rather
than limiting in nature. Variations and modifications to the
disclosed embodiment may become apparent to those skilled in the
art and do come within the scope of the invention. Accordingly, the
scope of legal protection afforded this invention can only be
determined by studying the following claims.
* * * * *