LAUSR

Two Ti-63.39Al-8.26Nb-0.2Y powders (powder 1 and powder 2) were fabricated by rapid in situ reaction and arc melting, respectively, then deposited on 316L stainless-steel substrate by the high-velocity oxygen fuel (HVOF) process. The phase composition, microstructure, porosity, microhardness, and adhesive strength of the two kinds of coating (DC1 and DC2) were characterized. DC1 had lower porosity, higher microhardness, and higher adhesive strength than DC2, which can be attributed to the difference in particle size distribution and mean particle size; a narrow particle size distribution and suitable mean particle size favor the formation of a HVOF coating with denser and more uniform microstructure. The thermal shock behavior was investigated by heating and water quenching from 600 °C to room temperature. The results showed that the failure of both TiAlNb coatings occurred due to spallation of the top coat, but the thermal shock resistance of DC2 was better than that of DC1. Thermal stress concentration caused by thermal expansion mismatch between the top coat and substrate was recognized as the major reason for TiAlNb coating failure.