Improvement in the oxidation resistance of Nb-16Si-24Ti-2Al-2Cr alloy by hot pressing

Nb-Si based alloy is a promising structural material due to its low density and remarkable high-temperature strength, while the poor oxidation resistance comes to a critical factor for its application. In this study, hot pressing (HP) method has been utilized to produce Nb-Si based alloys with fine microstructure to improve the high-temperature oxidation resistance. The effects of sintering temperature on the microstructural evolution and oxidation resistance of the Nb-16Si-24Ti-2Al-2Cr (at. %) alloys were investigated. Results show that, as the sintering temperature increased, the microstructure was refined at first and then coarsened. Correspondingly, the oxidation resistance of the alloy was enhanced at first and then decreased. The alloy sintered at 1400 C had the best oxidation resistance. In comparison to the as-cast alloy with relatively coarse microstructure, the current 1400 degrees C sintered alloy exhibited lower weight gain (150.74 mg/cm(2)) after oxidation at 1250 degrees C for 50 h, and the oxidation rate constant was decreased by similar to 53.3%. The primary reason for the improving oxidation resistance was attributed to the refined microstructure, which facilitated the formation of a more continuous and protective glassy SiO2 layer, thus safeguarding the alloy substrate from oxidation. This study provides new idea for the preparation of Nb-Si based alloys with high oxidation resistance in terms of microstructure refinement.