TREA

Method for laser/plasma surface alloying

Follow

Information

  • Patent Grant
  • 6229111
  • Patent Number
    6,229,111
  • Date Filed
    Wednesday, October 13, 1999
    25 years ago
  • Date Issued
    Tuesday, May 8, 2001
    23 years ago
Information
Abstract
The present invention is directed toward a method for plasma assisted laser surface alloying. Specifically, the present invention is directed toward a method for surface alloying using a laser beam having a rectangular cross sectional area and a plasma arc, in order to produce an alloyed substrate on the surface of the material.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention is directed toward a method for plasma assisted laser surface alloying. Specifically, the present invention is directed toward a method for surface alloying using a laser beam having a rectangular cross sectional area and a plasma arc, in order to produce an alloyed substrate on the surface of the material.




2. Description of the Prior Art




Laser beams have been used to irradiate the surface of a material coated with preselected alloying elements in order to produce a substrate having enhanced physical and/or metallurgical characteristics. The speed with which the surface of a material may be processed by laser alloying is a function of the thermal energy input produced by the laser. Greater processing speeds require more powerful and more expensive lasers.




The processing speed with which a material can be laser alloyed is also a function of the width of the laser beam used for alloying. Producing a laser beam having a greater cross sectional area, while maintaining a constant power density requires a larger and more expensive laser.




Plasma arcs have been used in the field of laser welding to provide increased energy input to the weld area without the power expenditure needed to produce an equivalent increase in energy input using only a laser. Prior art plasma assisted welding techniques have used a laser beam having a circular cross sectional area.




The present invention provides a plasma arc assisted method of laser alloying in which a plasma arc is used in conjunction with a laser beam having a rectangular cross sectional area. The plasma arc provides additional energy input resulting in an increase in processing speed, without the corresponding increase in cost that would result from using a more powerful laser to produce the increased energy input. Additionally, the plasma arc results in additional heating to the zone surrounding the melt region, thereby reducing the thermal gradient between the melt region and the adjacent regions of the material that is being processed. This reduced thermal gradient results in a reduced cooling rate which is regarded as advantageous.




SUMMARY OF THE INVENTION




The present invention is directed toward a method for laser/plasma surface alloying. This method comprises applying a precursor layer comprising a binder and a ceramic or metallic powder comprising chromium or silicon carbide to the surface of a metal substrate. The invention further comprises irradiating the surface of a substrate with a laser beam having a rectangular cross sectional area. The irradiation takes place at a sufficient energy level and for a sufficient time to melt a portion of the substrate such that it forms an alloy with the precursor.




The invention further comprises directing an uncollimated plasma arc to the surface of the substrate at the same time and location as the irradiating with the laser beam. While the irradiation takes place, the substrate is moved relative to the laser beam and the plasma arc.











DESCRIPTION OF THE FIGURES





FIG. 1

are block diagrams of the first embodiment of the present invention.





FIG. 2

are block diagrams of the second embodiment of the present invention.





FIG. 3

is an isometric view of an apparatus for practicing the present invention.





FIG. 4

is an enlarged top view of a laser beam cross sectional area for use in practicing the present invention.





FIGS. 5



a


-


5




d


are side views of four embodiments of the laser beams and plasma arc of the present invention at various angular orientations.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




A first embodiment of the present invention is directed toward a method for laser/plasma surface alloying. The invention comprises applying a precursor layer comprising a binder and a ceramic or metallic powder comprising chromium or silicon carbide to the surface of the metal substrate


39


, as shown in Block


10


of FIG.


1


and in FIG.


3


.




The invention further comprises irradiating the surface of the substrate with a laser beam


30


having an oval/rectangular cross sectional area as shown in

FIGS. 3-4

. The term “oval/rectangular”, as used herein, refers to a cross sectional area comprising two straight parallel sides and two opposing curved edges connecting the parallel sides, such that if the curved edges were replaced with straight edges, the cross sectional area would be rectangular. The irradiating takes place at a sufficient energy and for a sufficient time to melt a portion of the substrate, such that it forms an alloy with the precursor, as shown in Block


12


of FIG.


1


.




In one preferred embodiment, the laser beam is generated by a carbon dioxide laser having a power level of at least 400 watts. In another preferred embodiment, the laser beam is generated by a Nd:YAG laser as shown in FIG.


3


.




A preferred embodiment of the laser beam cross sectional area is shown in FIG.


4


. The laser beam


30


has a cross sectional area comprising two curved edges


32


and two straight sides


34


. The distance between the straight sides is referred to as the “beam width”. The distance between opposing curved edges along the axis which bisects the beam width is referred to as “beam length”. In one preferred embodiment, the length of each parallel side is at least four times the beam width. In another preferred embodiment, the length of each parallel side is less than or equal to 10 times the beam width.




The invention further comprises directing an uncollimated plasma arc


42


to the surface of the substrate at the same time and location as the irradiating with the laser beam, as shown in Block


14


of FIG.


1


. In a preferred embodiment, a plasma torch


40


is used to generate the plasma arc


42


. In another preferred embodiment, the plasma arc has a current level of at least 25 amperes.




The invention further comprises moving the substrate relative to the laser beam and plasma arc, as shown in Block


16


of FIG.


1


. In a preferred embodiment, the substrate is moved relative to the laser beam and plasma arc at a translation rate of at least 100 millimeters per minute, as shown in FIG.


3


. The translation axis along which the laser beam and plasma arc are moved relative to the substrate is labeled


36


in FIG.


3


.




The axis


36


on

FIG. 3

is labeled with a “+” and a “−” sign to denote movement in either direction along the axis. When the substrate is moved in the − direction, it will be irradiated first by the plasma arc and then be irradiated by the laser. This embodiment of the invention is referred to as “plasma leading”. When the substrate is moved in the + direction, along the translation axis, it will be irradiated first by the laser and then be irradiated by the plasma arc. This embodiment of the invention is referred to as “laser leading”.




The translation axis direction depicted in

FIG. 3

is referred to herein as the “y axis”. The axis perpendicular to the y axis is referred to as the “x axis”. The distance in the y axis directions between an axis which bisects the laser beam in the width dimension and a parallel axis which bisects the plasma arc is referred to as “Δy”. In the plasma leading environment, the ratio of Δy to laser beam width should be less than or equal to 4.28. In the laser leading embodiment, the ratio of Δy to laser beam width should be less than or equal to 0.89.




In

FIG. 3

, dotted line


50


represents an axis in the y dimension which bisects the laser beam in its length dimension. In

FIG. 3

, dotted line


52


represents an axis in the y dimension which bisects the plasma arc. As shown in

FIG. 3

, axis


52


is parallel to axis


50


. The displacement in the x dimension between axis


50


and axis


52


is referred to as “Δx”. The ratio of Δx to laser beam length should be less than or equal to 0.156.




Another embodiment of the present invention is depicted in FIG.


2


. As shown in Blocks


18


,


20


,


22


and


24


of

FIG. 2

, this embodiment of the invention is directed toward the use of a laser beam having a rectangular cross sectional area in which the longer sides of the rectangular cross sectional area are at least four times as long as the shorter sides of the rectangular cross sectional area and in which the substrate is moved at a translation rate of at least 100 millimeters per minute relative to the plasma arc and the laser beam.




The angular orientations of the laser beam and the plasma arc with respect to the substrate alpha (α) and beta (β), respectively, can be varied, as shown in

FIGS. 5



a


-


5




d


. In one preferred embodiment, α and β are 90° and 45°, respectively, as shown in FIG.


5




b


. In another preferred embodiment, α and β are 70° and 70°, respectively, as shown in

FIG. 5



c


. In a third embodiment, α and β are 45° and 90° respectively.




The foregoing disclosure and description of the invention are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction may be made without departing from the spirit of the invention.



Claims
  • 1. A method for laser/plasma surface modification comprising:a. applying a precursor layer comprising a binder and a ceramic or metallic powder to the surface of a metal substrate; b. irradiating the surface of the substrate with a laser beam having a rectangular/oval cross sectional area defined by two straight parallel sides separated by a distance defined as the beam width and comprising two opposing curved edges connecting the parallel sides, wherein the distance between opposing curved edges along an axis which bisects the beam width is the beam length, said irradiation taking place at a sufficient energy level and for a sufficient time to melt a portion of said substrate such that it forms an alloy with said precursor; c. directing an uncollimated plasma arc to the surface of the substrate at a position such that the distance between an axis which bisects the laser beam in the length dimension and a parallel axis which bisects the plasma arc is defined as Δx and the ratio of Δx/beam length is less than or equal to 0.156 and wherein the distance between an axis which bisects the laser beam in the width dimension and a parallel axis which bisects the plasma arc is defined as Δy and the ratio of Δy/beam width is less than or equal to 4.28, and wherein said directing occurs at the same time as the irradiating with the laser beam; and d. moving said substrate relative to said laser beam and said plasma arc along a translation axis in a direction such that the substrate will be irradiated first by the plasma arc and then be irradiated by the laser beam.
  • 2. The method of claim 1, wherein a plasma torch is used to generate the plasma arc.
  • 3. The method of claim 1, wherein said laser beam is generated by a carbon dioxide laser having a power level of at least 400 watts.
  • 4. The method of claim 3, wherein said plasma arc has a current level of at least 25 amperes.
  • 5. The method of claim 1, wherein said substrate is moved relative to said laser and said plasma at a speed of at least 100 millimeters per minute.
  • 6. The method of claim 1, wherein the length of each of said parallel sides, is at least 4 times the beam width.
  • 7. The method of claim 6, wherein the length of each of said parallel sides is less than or equal to ten times the beam width.
  • 8. The method of claim 1 wherein said powder comprises chromium or silicon carbide.
  • 9. A method for laser/plasma surface modification comprising:a. applying a precursor layer comprising a binder and a ceramic or metallic powder to the surface of a metal substrate; b. irradiating the surface of the substrate with a laser beam having a rectangular/oval cross sectional area defined by two straight parallel sides separated by a distance defined as the beam width and comprising two opposing curved edges connecting the parallel sides, wherein the distance between opposing curved edges along an axis which bisects the beam width is the beam length, said irradiation taking place at a sufficient energy level and for a sufficient time to melt a portion of said substrate such that it forms an alloy with said precursor; d. directing an uncollimated plasma arc to the surface of the substrate at a position such that the distance between an axis which bisects the laser beam in the length dimension and a parallel axis which bisects the plasma arc is defined as Δx and the ratio of Δx/beam length is less than or equal to 0.156 and wherein the distance between an axis which bisects the laser beam in the width dimension and a parallel axis which bisects the plasma arc is defined as Δy and the ratio of Δy/beam width is less than or equal to 0.89, and wherein said directing occurs at the same time as the irradiating with the laser beam; and d. moving said substrate relative to said laser beam and said plasma arc along a translation axis in a direction such that the substrate will be irradiated first by the laser beam and then be irradiated by the plasma arc.
  • 10. The method of claim 9, wherein a plasma torch is used to generate the plasma arc.
  • 11. The method of claim 9, wherein said laser beam is generated by a carbon dioxide laser having a power level of at least 400 watts.
  • 12. The method of claim 11, wherein said plasma arc has a current level of at least 25 amperes.
  • 13. The method of claim 9, wherein said substrate is moved relative to said laser and said plasma at a speed of at least 100 millimeters per minute.
  • 14. The method of claim 9, wherein the length of each of said parallel sides, is at least 4 times the beam width.
  • 15. The method of claim 14, wherein the length of each of said parallel sides is less than or equal to ten times the beam width.
  • 16. The method of claim 9 wherein said powder comprises chromium or silicon carbide.
  • 17. A method for plasma assisted laser surface alloying comprising:a. applying a precursor layer comprising a binder and a ceramic or metallic powder to the surface of a metal substrate; b. irradiating the surface of the substrate with a laser beam having a rectangular/oval cross sectional area defined by two straight parallel sides separated by a distance defined as the beam width and comprising two opposing curved edges connecting the parallel sides, wherein the distance between opposing curved edges along an axis which bisects the beam width is the beam length, said irradiation taking place at a sufficient energy level and for a sufficient time to melt a portion of said substrate such that it forms an alloy with said precursor; c. directing an uncollimated plasma arc to the surface of the substrate at a position such that the distance between an axis which bisects the laser beam in the length dimension and a parallel axis which bisects the plasma arc is defined as Δx and the ratio of Δx/beam length is less than or equal to 0.156 and wherein the distance between an axis which bisects the laser beam in the width dimension and a parallel axis which bisects the plasma arc is defined as Δy and the ratio of Δy/beam width is less than or equal to 0.89, and wherein said directing occurs at the same time as the irradiating with the laser beam; and d. moving said substrate relative to said laser beam and said plasma arc at a speed of at least 100 millimeters per minute.
  • 18. The method of claim 17, wherein said laser beam is generated by a carbon dioxide laser having a power level of at least 400 watts.
  • 19. The method of claim 17 wherein said laser beam is generated by an Nd:YAG laser.
  • 20. The method of claim 17 wherein said powder comprises chromium or silicon carbide.
US Referenced Citations (69)
Number Name Date Kind
3705758 Haskal Dec 1972
3848104 Locke Nov 1974
3986767 Rexer et al. Oct 1976
4015100 Gnanamuthu et al. Mar 1977
4017708 Engel et al. Apr 1977
4157923 Yen et al. Jun 1979
4212900 Serlin Jul 1980
4322601 Serlin Mar 1982
4434189 Zaplatynsky Feb 1984
4475027 Pressley Oct 1984
4480169 Macken Oct 1984
4495255 Draper et al. Jan 1985
4535218 Krause et al. Aug 1985
4617070 Amende et al. Oct 1986
4638163 Braunlich et al. Jan 1987
4644127 La Rocca Feb 1987
4689467 Inoue Aug 1987
4720312 Fukuizumi et al. Jan 1988
4724299 Hammeke Feb 1988
4746540 Kawasaki et al. May 1988
4750947 Yoshiwara et al. Jun 1988
4801352 Piwczyk Jan 1989
4839518 Braunlich et al. Jun 1989
4847112 Halleux Jul 1989
4898650 Wu et al. Feb 1990
4904498 Wu Feb 1990
4964967 Hashimoto et al. Oct 1990
4981716 Sundstrom Jan 1991
4998005 Rathi et al. Mar 1991
5059013 Jain Oct 1991
5095386 Scheibengraber Mar 1992
5124993 Braunlich et al. Jun 1992
5130172 Hicks et al. Jul 1992
5147999 Dekumbis et al. Sep 1992
5196672 Matsuyama et al. Mar 1993
5208431 Uchiyama et al. May 1993
5230755 Pierantoni et al. Jul 1993
5247155 Steen et al. Sep 1993
5257274 Barrett et al. Oct 1993
5265114 Sun et al. Nov 1993
5267013 Spence Nov 1993
5290368 Gavigan et al. Mar 1994
5308431 Maher et al. May 1994
5314003 Mackay May 1994
5319195 Jones et al. Jun 1994
5321224 Kamimura et al. Jun 1994
5322436 Horng et al. Jun 1994
5331466 Van Saarloos Jul 1994
5352538 Takeda et al. Oct 1994
5387292 Morishige et al. Feb 1995
5406042 Engelfriet et al. Apr 1995
5409741 Laude Apr 1995
5411770 Tsai et al. May 1995
5430270 Findlan et al. Jul 1995
5446258 Mordike Aug 1995
5449536 Funkhouser et al. Sep 1995
5466906 McCune, Jr. et al. Nov 1995
5484980 Pratt et al. Jan 1996
5486677 Maischner et al. Jan 1996
5491317 Pirl Feb 1996
5514849 Findlan et al. May 1996
5530221 Benda et al. Jun 1996
5546214 Black et al. Aug 1996
5563095 Frey Oct 1996
5614114 Owen Mar 1997
5643641 Turchan et al. Jul 1997
5659479 Duley et al. Aug 1997
5874011 Ehrlich Feb 1999
6133541 Neubauer et al. Oct 2000
Foreign Referenced Citations (14)
Number Date Country
4126351 Feb 1993 DE
199 41 563 Aug 2000 DE
876870A1 Apr 1998 EP
903423 Mar 1999 EP
279692 Nov 1988 JP
401083676A Mar 1989 JP
381082 Apr 1991 JP
3115587A May 1991 JP
403115531A May 1991 JP
5285686 Nov 1993 JP
1557193 Apr 1990 SU
1743770 Jun 1992 SU
WO 9521720 Aug 1995 WO
WO 9747397 Dec 1997 WO
Non-Patent Literature Citations (48)
Entry
Ayers, et al.; “A Laser Processing Technique for Improving the Wear Resistance of Metals,” Journal of Metals, Aug. 1981, 19-23.
Belvaux, et al.; “A Method for Obtaining a Uniform Non-Gaussian Laser Illumination,” Optics Communications, vol. 15, No. 2, Oct. 1975, 193-195.
Bett, et al.; “Binary phase zone-plate arrays for laser-beam spatial-intensity distribution conversion,” Applied Optics, vol. 34, No. 20, Jul. 10, 1995, 4025-4036.
Bewsher, et al.; “Design of single-element laser-beam shape projectors,” Applied Optics, vol. 35, No. 10, Apr. 1, 1996, 1654-1658.
Breinan, et al.; “Processing material with lasers,” Physics Today, Nov. 1976, 44-50.
Bruno, et al.; “Laserbeam Shaping for Maximum Uniformity and Maximum Loss, A Novel Mirror Arrangement Folds the Lobes of a Multimode Laserbeam Back onto its Center,” Lasers & Applications, Apr. 1987, 91-94.
Chen, et al.; “The Use of a Kaleidoscope to Obtain Uniform Flux Over a Large Area in a Solar or Arc Imaging Furnace,” Applied Optics, vol. 2, No. 3, Mar. 1963, 265-571.
Christodoulou, et al.; “Laser surface melting of some alloy steels,” Metals Technology, Jun. 1983, vol. 10, 215-222.
Cullis, et al.; “A device for laser beam diffusion and homogenisation,” J. Phys.E:Sci. Instrum., vol. 12, 1979, 688-689.
Dahotre, et al., “Development of microstructure in laser surface alloying of steel with chromium,” Journal of Materials Science, vol. 25, 1990, 445-454.
Dahotre, et al., “Laser Surface Melting and Alloying of Steel with Chromium,” Laser Material Processing III, 1989, 3-19.
Fernelius, et al.; “Design and Testing of a Refractive Laser Beam Homogenizer,” Airforce Writing Aeronautical Laboratories Report, (AFWAL-TR-84-4042), Sep. 1984, 46 pages.
Frieden; “Lossless Conversion of a Plane Laser Wave to a Plane Wave of Uniform Irradiance,” Applied Optics, vol. 4, No. 11, Nov. 1965, 1400-1403.
Galletti, et al.; “Transverse-mode selection in apertured super-Gaussian resonators: an experimental and numerical investigation for a pulsed CO 2 Doppler lidar transmitter,” Applied Optics, vol. 36, No. 6, Feb. 20, 1997, 1269-1277.
Gori, et al.; “Shape-invariance range of a light beam,” Optics Letters, vol. 21, No. 16, Aug. 15, 1996, 1205-1207.
Grojean, et al.; “Production of flat top beam profiles for high energy lasers,” Rev. Sci. Instrum. 51(3), Mar. 1980, 375-376.
Hella, “Material Processing with High Power Lasers,” Optical Engineering, vol. 17, No. 3, May-Jun. 1978, 198-201.
Ignatiev, et al.; “Real-time pyrometry in laser machining,” Measurement and Science Technology, vol. 5, No. 5, 563-573.
“Laser Removing of Lead-Based Paint” Illinois Department of Transportation, Jun. 1992, 26 pages.
Jones, et al.; “Laser-beam analysis pinpoints critical parameters,” Laser Focus World, Jan. 1993, 123-130.
Khanna, et al.; “The Effect of Stainless Steel Plasma Coating and Laser Treatment on the Oxidation Resistance of Mild Steel,” Corrosion Science, vol. 33, No. 6, 1992, 949-958.
“New Products” Laser Focus World, Aug. 1996, 173.
Lugscheider, et al.;“ A Comparison of the Properties of Coatings Produced by Laser Cladding and Conventional Methods,” Surface Modification Technologies V, The Institute of Materials, 1992, 383-400.
Manna, et al.; “A One-dimensional Heat Transfer Model for Laser Surface Alloying of Chromium on Copper Substrate,” Department of Metallurgical & Materials Engineering, Indian Institute of Technology, vol. 86, n. 5, May 1995, 362-364.
Mazille, et al.; “Surface Alloying of Mild Steel by Laser Melting of Nickel and Nickel/Chromium Precoatings,” Materials Performance Maintenance, Aug. 1991, 71-83.
Molian; “Characterization of Fusion Zone Defects in Laser Surface Alloying Applications,” Scripta Metallurgica, vol. 17, 1983, 1311-1314.
Molian; “Effect of Fusion Zone Shape on the Composition Uniformity of Laser Surface Alloyed Iron,” Scripta Metallurgica, vol. 16, 1982, 65-68.
Molian; Structure and hardness of laser-processed Fe-0.2%C-5%CR and Fe-0.2%C-10%Cr alloys; Journal of Materials Science, vol. 20, 1985, 2903-2912.
“Line-Focussing Optics for Multiple-Pass Laser Welding,” NASA Tech Briefs MFS-29976, date unknown.
“Cylindrical Lenses,” Newport Technical Guide, date unknown, N-65.
“Fused Silica Cylindrical Lenses,” Newport Technical Guide,. date unknown, N-68.
Oswald, et al.; “Measurement and modeling of primary beam shape in an ion microprobe mass analyser,” IOP Publishing Ltd., 1990, 255-259.
Renaud, et al., “Surface Alloying of Mild Steel by Laser Melting of an Electroless Nickel Deposit Containing Chromium Carbides,” Materials & Manufacturing Processes, 6(2), 1991, 315-330.
Smurov, et al.; “Peculiarities of pulse laser alloying: Influence of spatial distribution of the beam,” J. Appl. Phys. 71(7), Apr. 1, 1992, 3147-3158.
“Spawr Integrator,” Spawr Optical Research, Inc., Data Sheet No. 512, Jun. 1986.
Veldkamp, et al.; “Beam profile shaping for laser radars that use detector arrays,” Applied Optics, vol. 21, No. 2, Jan. 15, 1982, 345-358.
Veldkamp; “Laser Beam Profile Shaping with Binary Diffraction Gratings,” Optics communications, vol. 38, No. 5,6, Sep. 1, 1981, 381-386.
Veldkamp; “Laser beam profile shpaing with interlaced binary diffraction gratings,” Applied Optics, vol. 21, No. 17, Sep. 1, 1982, 3209-3212.
Veldkamp; “Technique for generating focal-plane flattop laser-beam profiles,” Rev. Sci. Instru., vol. 53, No. 3, Mar. 1982, 294-297.
Walker, et al.; “Laser surface alloying of iron and 1C-1•4CR steel with carbon,” Metals Technology, vol. 11, Sep. 1984, 5 pages.
Walker, et al.; “The laser surface-alloying of iron with carbon,” Journal of Material Science vol. 20, 1985, 989-995.
Wei, et al.; “Investigation of High-Intensity Beam Characteristics on Welding Cavity Shape and Temperature Distribution,” Journal of Heat Transfer, vol. 112, Feb. 1990, 163-169.
Charschan, “Lasers in industry,” Laser Processing Fundamentals, (Van Nostrand Reinhold Company), Chapter 3, Sec. 3-1, 139-145.
Fernelius, et al; “Calculations Used in the Design of a Refractive Laser Beam Homogenizer,” Airforce Writing Aeronautical Laboratories Report, (AFWAL-TR-84-4047), Aug. 1984, 18 pages.
Jain, et al.; “Laser Induced Surface Alloy Formation and Diffusion of Antimony in Aluminum,” Nuclear Instruments and Method, vol. 168, 275-282, 1980.
Molian; “Estimation of cooling rates in laser surface alloying processes,” Journal of Materials Science Letters, vol. 4, 1985, 265-267.
“High Power CW Nd:YAG Laser Transformation Hardening,” Hobart Laser Products, 2 pages.
ASM Handbook, vol. 6, Welding, Brazing, and Soldering, 1993.