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 produced on nickel and on iron based substrates, respectively. A continuous wave carbon dioxide laser and two separate powder feeders were employed. 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 layers with various Al contents were first produced in order to obtain fundamental data required for the processing of functionally graded materials. Functionally graded Ni-Al and Fe-Al coatings (up to three layers) were produced by successive deposition of clad layers normal to the substrate surface. Compositional control was achieved by keeping the powder flow of Ni or Fe constant and changing the flow rate of Al. Microstructures are interpreted and discussed in relation to aluminides based on the Ni-Al and Fe-Al systems.