Dezhi Chen, Wotai Gong, Xiaofu Zhang, Chao Xu, Dongxin Wang, Shuo Yin, Ruirun Chen
The oxidation resistance and behavior of Nb-16Si-20Ti-1.5Zr-1B-1C- x Gd ( x = 0.05, 0.1, 0.2, 0.4 at.%) alloys at 1250 °C were investigated. A suitable Gd addition (0.2 at.%) effectively refines the microstructure. Oxidation tests reveal that the alloy with 0.2 at.% Gd exhibits the best oxidation resistance, with a weight gain of 166.7 mg/cm² after 50 h at 1250 °C, which is 39.2% lower than that of the 0.05 at.% Gd alloy (274.4 mg/cm²). During oxidation, Gd 2 O 3 reacts with Nb 2 O 5 and TiO 2 to form GdNbTiO 6 , which exists at phase boundaries and impedes the inward diffusion of oxygen. Moreover, a refined microstructure reduces the oxidation rate and enhances the oxide-scale density. Therefore, appropriate Gd addition (0.2 at.%) enhances oxidation resistance by promoting GdNbTiO 6 formation and microstructure refinement.