Microstructures and high-temperature oxidation behavior of directionally solidified Nb–Si-based alloys with Re additions

High-temperature oxidation behavior of directionally solidified (DS) Nb–Si-based alloys with Re additions was investigated at 1200 and 1250 °C, respectively. Microstructures and high-temperature oxidation behavior of the alloys were characterized. Results show that the microstructures in vertical section of Nb–24Ti–15Si–4Cr–2Al–2Hf–xRe (x = 0, 1, 3; at%) alloys grow parallel to the withdrawal direction and the cross section exhibits bud-like structures. The bud-like structures become finer with more Re additions. The weight gain of the Nb–24Ti–15Si–4Cr–2Al–2Hf–3Re alloy after oxidation at 1200 °C for 100 h is 198.1 mg·cm⁻², and it is a bit higher at 1250 °C. The other two alloys perform somewhat worse. The influence of Re addition on the oxidation resistance at 1250 °C is more significant than that at 1200 °C. Although Re addition does not benefit obviously the high-temperature oxidation resistance of the DS samples, it does not compromise the oxidation resistance with a certain amount of Re additions in contrast with the alloy without Re addition.