Interdiffusion behavior of Mo-Si-B/Al2O3 composite coating on Nb-Si based alloy

Abstract Mo-Si-B/Al2O3 composite coating was applied to Nb-Si based alloys by plasma spray-physical vapor deposition (PS-PVD) followed by spark plasma sintering (SPS). Interdiffusion behavior of the coating at 1200, 1250 and 1300 °C in dry air was investigated. The results indicate that the thickness of the interdiffusion zone (IDZ) in the composite coating is smaller than that in the Al2O3-free coating. The Al2O3 diffusion barrier effectively restrains coating-substrate interdiffusion. The activation energy for IDZ growth is increased to 367 kJ/mol correspondingly, and the interdiffusion coefficient of Si is decreased by one order of magnitude.