Effect of Zr content on the structure and oxidation resistance of silicide coatings prepared by pack cementation technique

Modified silicide coatings were prepared on Ti-5Al-10Nb-xZr (x = 0, 2, 5, 10, 15 and 20 at.%) alloys by pack cementation process. The effects of Zr content on the coating structure and oxidation resistance have been investigated. With increasing Zr contents in the substrate, the coating structure shows a significant change. Adding 2 at.% Zr can improve the oxidation resistance of silicide coating due to the formation of a thin and dense SiO2 layer. But excessive Zr exerts an adverse influence on the oxidation resistance due to the volume expansion caused by the phase transformation of ZrO2 during the oxidation process.