FUNCTIONALLY GRADED NICKEL-ALUMINIDE AND IRON-ALUMINIDE COATINGS PRODUCED VIA LASER CLADDING

Functionally graded nickel-aluminide and iron-aluminide in the form of superimposed clad layers up to similar to 4 mm total thickness were p roduced on nickel and on iron based substrates, respectively. A contin uous wave carbon dioxide laser and two separate powder feeders were em ployed. The processing parameters were: 1.8 kW laser power, 3 mm beam diameter, and 7 mm s(-1) traverse speed. A series of single clad layer s with various Al contents were first produced in order to obtain fund amental data required for the processing of functionally graded materi als. Functionally graded Ni-Al and Fe-Al coatings (up to three layers) were produced by successive deposition of clad layers normal to the s ubstrate surface. Compositional control was achieved by keeping the po wder flow of Ni or Fe constant and changing the flow rate of Al. Micro structures are interpreted and discussed in relation to aluminides bas ed on the Ni-Al and Fe-Al systems.