测试了不同B含量(5%~17%,原子分数)的Mo-Si-B合金在1000~1300 ℃的抗氧化性能,并对其微观组织及抗氧化机制进行了分析。结果表明,Mo-Si-B合金的氧化行为受B含量和氧化温度共同影响,B元素主要通过改善表面玻璃相流动性和调节合金内α-Mo、Mo₃Si和Mo₅SiB₂三相的体积分数和微观组织来影响氧化膜的形成和生长过程。B含量的增加虽然有助于提升玻璃相在低温下的流动性而促使表面氧化膜快速成形和均匀覆盖,但在高温下氧化膜充足的流动性却不利于合金抗氧化性能的提升。在低温时Mo-Si-B合金的抗氧化性能受控于B含量,而在高温时抗氧化性能取决于α-Mo相含量。对于B含量较高的细晶Mo-12Si-17B合金,由于含有较多的Mo₅SiB₂相和较少的α-Mo相,在1000~1300 ℃整个氧化温度区间内,表面均能形成一层完整、致密的氧化膜。金属间化合物弥散分布的细晶结构可以确保Mo-Si-B合金表现出优异的抗氧化性能。

The oxidation behaviors of the Mo-Si-B alloy with B content in the range of 5% to 17% (atomic fraction) were experimentally investigated at temperatures ranging from 1000 ℃ to 1300 ℃. The microstructures and antioxidant mechanisms were also analyzed. Results showed that the oxidation behaviors were affected by both B content and oxidation temperature. The formation and growth process of oxidation film were mainly influenced by the B element which could improve the fluidity of surface glass phase and adjust the volume fraction and microstructure of α-Mo, Mo₃Si and Mo₅SiB₂. The Mo-Si-B alloy with the B content increasing was favourable for quick forming and uniform covering by improving the mobility of the glass, but which decreased the oxidation resistance due to the sufficient liquidity of the oxidation film at high temperature. The oxidation resistance of the Mo-Si-B alloy is controlled by B content at low temperature and α-Mo content at high temperature, respectively. A large quantity of Mo₅SiB₂ phase and a small quantity of α-Mo phase existed in the high B content of Mo-12Si-17B alloy, which could promote the oxide layer to form rapidly but also cover uniformly under the temperature range of 1000~1300 ℃. The discussion illustrates that the fine-grained microstructure combining with the distributed intermetallics is a specific role to ensure the excellent oxidation resistance of Mo-Si-B alloy.