Microstructure and Oxidation Resistance of Y Modified Silicide Coatings Prepared on Zr-Ti-Al Alloy

Abstract

Zr-20Ti-5Al (at. %) alloy used as substrates for Si-Y2O3co-deposition experiments was prepared by firstly vacuum non-consumable arc melting and then high frequency induction skull melting. The results showed that Y modified silicide coating prepared at 1250 °C for 4 h possessed a double-layer structure, mainly consisting of a thick (Zr, Ti)Si2outer layer and a 15 mm thick (Zr, Ti)Si inner layer. Meanwhile, the growth rate of ZrSi2phase changed with temperature, while the growth rate of ZrSi did not vary significantly with temperature. The growth of the coating as well as the two layers followed parabolic laws, and the co-deposition process was controlled by diffusion. ZrSi2was not appropriate as oxidation-resistant coatings to protect Nb based alloy from oxidation due to the lack of the formation of good quality glassy SiO2layer in the scale.