Avco Everett Research Laboratory, Inc.

Daniel S Gnanamuthu

Edward V Locke

Properties of the surface of low melting substrate parts including low melting, high conductivity reactive metal parts, are modified by forming an alloy casing thereon having the metal of the substrate as a first (matrix) component thereof together with a higher melting material as the second (reinforcing) component. The higher melting component is coated on the substrate, melted under laser heating, with gas shielding to avoid oxidation, and mixed with a melted portion of the substrate through convective circulation and the mixture is rapidly cooled to produce the alloy casing. Then the casing may be rescanned with the laser beam to rapidly melt and resolidify the casing with refined grain structure. Such grain refining may also be applied to uncoated substrates.

Metal surface modification

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.

Surface modification

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.

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Weymouth, MA, United States of America

Daniel S Gnanamuthu