Surface modification

• US 4,015,100 A
• Filed: 09/08/1975
• Issued: 03/29/1977
• Est. Priority Date: 01/07/1974
• Status: Expired due to Term

• Current Assignee: Combustion Engineering Incorporated (ABB Limited)
• Original Assignee: Avco Everett Research Laboratory, Inc. (Textron Inc)
• Inventors: Gnanamuthu, Daniel S., Locke, Edward V.
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Shaw, Clifford C.
• Application Number:
  US05/611,628
• Time in Patent Office: 568 Days
• Field of Search: 219/121 L, 219/121 LM, 219/121 EB, 219/121 EM, 219/121 P, 219/76, 219/137, 29/156.7 R, 29/156.7 A, 148/3, 148/4, 148/6, 148/13
• US Class Current: 148/512
• CPC Class Codes: B23K 2103/02 Iron or ferrous alloys
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 2103/06 Cast-iron alloys
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/18 Dissimilar materials
• CPC Class Codes: B23K 2103/26 Alloys of Nickel and Cobalt and Chromium
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/32 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/34 Laser welding for purposes other than joining
• CPC Class Codes: B23K 26/342 Build-up welding
• CPC Class Codes: B23K 35/30 with the principal constituent melting at less than 1550 degrees C
• CPC Class Codes: C21D 1/09 by direct application of electrical or wave energy; by particle radiation
• CPC Class Codes: C22C 1/02 by melting C22C1/1036 takes precedence
• CPC Class Codes: Y10S 148/903 Directly treated with high energy electromagnetic waves or particles, e.g. laser, electron beam

Abstract

Properties of a surface layer of a metal part are modified by changing its composition and microstructure using focused radiant energy. Minor components of an alloy having the metal of the substrate as the major component thereof are applied to the surface and a limited depth surface layer of the substrate metal is melted, the coated-on components are mixed therewith and the mixture is rapidly cooled to produce a desired surfacing alloy to a controlled depth within the substrate and having a fine grained microstructure compared to the microstructure of the substrate metal. The amount of coated-on minor alloy components and the preselected depth of melting of the substrate metal provide alloy composition control. The melting is carried out by application of focused radiant energy using a laser, preferably applied in a manner to promote mixing of the coated-on minor alloy components and the molten substrate layer during the short time, on the order of tenths of a second, of molten state maintenance for any given surface area.

Claims

1. Surface layer production method comprising,

coating metal substrate with a coating layer comprising desired alloying ingredients,

relatively scanning a continuous wave laser beam of 1-20 kilowatts focused to a 0.025 to 0.7 inch diameter circle or area equivalent of other form over the coated surface in a linear trace at a rate of 5-500 inches per minute to melt the coating and a predetermined depth and width of the substrate surface along said linear trace and forcibly intermix the melted substrated layer and the entirety of the coating through mass transfer predominant over any diffusion mixing and rapidly cooling to produce a solid alloy casing and a substantial weight per cent of which is obtained from the substrate along said linear trace of the produced alloy composition throughout said predetermined depth,

the depth of melting being selected in relation to amount of minority alloying ingredients and the tine of residence in molten state and cooling rate and heat transfer conditions at said layer being controlled to produce a desired alloy composition and so that the secondary dendrite spacing of said alloy is 1-100 microns.

2. Method in accordance with claim 1 wherein a single linear trace of relative scan between substrate and laser beam is made.

3. Method in accordance with claim 1 wherein the laser beam is deflected.

4. Method in accordance with claim 1 wherein the substrate is scanned past the relatively static laser beam.

5. Method in accordance with claim 1 wherein the linear scan is along a closed loop path.

6. Method in accordance with claim 5 wherein power is ramped down at closing of the loop to prevent local heat buildup at the overlap of linear scan begin and completion.

7. Method is accordance with claim 1 wherein the alloyed layer depth is from 2-200 mils.

8. Method in accordance with claim 1 wherein the laser beam is locally oscillated at 100-1000 Hertz to promote mixing during said linear scan.

9. Surface layer production method in accordance with claim 1 wherein said casing has homogeneity of chemical composition and fine grain structure throughout its depth.