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

摘要

Zr-20Ti-5A1 (at. %) alloy used as substrates for Si-Y_2O_3 co-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)Si_2 outer layer and a 15 μm thick (Zr, Ti)Si inner layer. Meanwhile, the growth rate of ZrSi_2 phase 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. ZrSi_2 was not appropriate as oxidation-resistant coatings to protect Nb based alloy from oxidation due to the lack of the formation of good quality glassy SiO_2 layer in the scale.