Effects of Cr addition on the microstructures and oxidation of Nb-Si-Al-Ti-W alloys

摘要

The effects of Cr addition on the microstructures and oxidation kinetics of the Nb-20Si-5Al-15Ti-5W alloys have been investigated in this study. The alloys were prepared by Spark Plasma Sintering (SPS) technology. The results show that the microstructure of the alloys consists of (Nb, Ti, W)ss, α-Nb5Si3, γ-Nb5Si3 and (Nb, Ti)5Si3 phase. The addition of 3at% Cr improves the oxidation resistance of the composite at 800 °C and 1100°C dramatically. The AlNb_(11)O_(29), Ti2Nb_(10)O_(29), TiO2, Nb2O5, Cr2Ti6O_(15), and Nb4W3O_(47) are present in the scales formed at 800°C. The phases present in the oxide scales formed at 1100°C consisted of AlNb_(11)O_(29), Ti2Nb_(10)O_(29), TiO2, Cr2WO6, andNb2O5. The oxidation resistance of the composite at 1100°C is better than at 800 °C because the oxide scale is more compact structure.