【摘要】 采用扫描电镜研究了K403镍基铸造高温合金在850℃下,热暴露50~200 h后的微观组织,并分析了力学性能的变化。结果表明:热暴露前后的组织均为典型的树枝晶组织,热暴露后(γ+γ′)相共晶特征趋于不明显,MC碳化物部分发生分解,在枝晶间、晶界附近和碳化物周围析出有害的TCP脆性相即针状σ相,并且随着热暴露时间的延长,针状σ相析出量增多;合金的名义屈服强度和抗拉强度随热暴露时间的延长而下降,硬度略有提高,塑性降低;针状的σ脆性相的析出是导致合金力学性能下降的主要原因之一。更多还原

【Abstract】 The microstructure of Ni-based casting superalloy K403 after thermal exposure at 850 ℃ for 50-200 h were studied by SEM.And the mechanical properties were also analyzed.The results show that the microstructure of the alloy presents a typical dendritic structure before and after thermal exposure.However,after the thermal exposure,(γ+γ′)eutectic phase feature is not evident,and the part of MC carbides have decomposed,while the harmful TCP brittle phase namely acicular σ phase are also precipitated in the interdendritic regions,the grain boundary and the carbide surrounding,and with the prolonging time of the thermal exposure,acicular σ phase precipitation increases.With increasing the time,the offset yielding stress and tensile strength were reduced,while the hardness was improved slightly and the plasticity was reduced.The acicular σ brittle phase precipitation was one of the main reasons for the deterioration of alloy mechanical properties.更多还原