Microstructure and oxidation resistance of Ti modified Si-Mo coating on Nb-Si based ultrahigh temperature alloy

Ti modified Si-Mo coatings have been successfully prepared on Nb-Si based ultrahigh temperature alloy by slurry sintering method. The results show that the addition of Ti as well as its content has an obvious influence on the density, grain size and oxidation resistance of the coatings. The 5 at% Ti modified coating possesses the best oxidation protection performance with a multi-layered structure consisting of a C11b MoSi2/C40 (Mo,Ti)Si2 outer layer and a dense (Ti,Nb)5Si4/(Nb,X)5Si3 inner layer. After oxidation, the formation of SiO2 and TiO2 can quickly seal the holes in the coating and form a dense SiO2/TiO2 scale.