Environmental deterioration analysis of heat resisting alloys for the mono-propellant thruster

L-605合金具有高强度和高抗氧化性的优良组合，已被用作单组元推进剂结构和筛分材料。然而，L-605合金在含有氮气和氨气的高温环境中的劣化现象已有报道。因此，为了研究L-605合金在氮气气氛中的退化机理，对该合金在氮气气氛中热处理前后的成分、显微组织、硬度和拉伸性能进行了评价。热处理后合金中析出了氮化铬和碳化钨。这些析出物随着热处理时间的延长而增加。在氮气气氛中1173K、86.4K的热处理使L-605合金的抗拉强度和断裂伸长率降低。这些结果表明，氮化铬和碳化钨的形成是L-605合金变质的原因。

L-605 alloy has been used for the mono-propellant structure and screen materials because of its excellent combination of high strength and high oxidation resistance. However, deterioration of L-605 alloy in a high temperature environment with nitrogen and ammonia has been reported. Therefore, the composition, microstructure, hardness and tensile properties of L-605 alloy were evaluated with and without heat treatment in a nitrogen gas atmosphere in order to investigate the degradation mechanism of the alloy. The chromium nitride and the tungsten carbide were precipitated in the alloy after the heat treatment. These precipitates were increased with increasing heat treatment duration. Tensile strength and elongation to fracture of L-605 alloy were decreased with heat treatment at 1173K for up to 86.4ks in nitrogen gas atmosphere. These results indicate that the chromium nitride and tungsten carbide formations are causal factors of deterioration of L-605 alloy.