Phase structure, morphology evolution and protective behaviors of chemical vapor deposited (Ni, Pt)Al coatings.

A chemical vapor deposited (CVD) aluminizing process had been employed to deposit platinum modified aluminide coatings on the nickel-based single-crystal superalloys. The kinetics behavior, phase evolution, microstructure and chemical composition of the (Ni, Pt)Al coatings after oxidation and hot corrosion tests were studied in detail. After isothermal oxidation test, a protective α-Al 2 O 3 scale is formed on the coating surface and, two new phases of (Ni, Pt) 3 Al 4 and γ′-(Ni, Pt) 3 Al due to phase transformation reactions occur in the aluminide layer. The inward diffusion of Al element toward the substrate and, formation of micro-pores in the interface of aluminide layer and interdiffusion zone are probably the main degradation modes of the coating. Corrosive medium including of mixed of aviation fuels and artificial seawater has not serious deterioration of the coating after hot corrosion and furthermore a network of grain boundary ridges is still co-existed on the coating surface, although large of micro-pores and some of grain boundaries are appeared within the aluminide layer. [ABSTRACT FROM AUTHOR]