Cavitation erosion mechanism of NiTi coatings made by laser plasma hybrid spraying

NiTi intermetallic compound is known to be a high cavitation erosion-resistant material. The erosion behaviors of NiTi intermetallic compound coatings made by laser plasma hybrid spraying (LPHS) were studied. The erosion resistance of the NiTi coatings depended strongly on the chemical composition of the coatings and the laser irradiation condition, because the NiTi phase and the microstructure of the coatings were varied by those conditions. The best erosion-resistant coatings were obtained with the conditions of nickel composition richer than that of equiatomic NiTi and irradiated laser power density greater than 6×10 8 W/m 2. The cavitation erosion resistance of the coating was about 380-fold that of a titanium alloy substrate. High erosion resistance of these coatings was obtained due to a combination of two factors, namely, super elasticity due to austenite-phase NiTi and high work hardenability due to excess soluble Ni.