The combination of stress and hot corrosion may result in Ni-base superalloys experiencing stress corrosion cracking, of which, the mechanisms are little understood. The aim of this research was to enhance the understanding by performing a series of stress corrosion exposures, at temperatures of 550, 500 and 450 °C, on: CMSX-4, CM247LC DS and IN6203DS superalloys. After completing the exposures, the superalloys were ranked with respect to the severity of the cracking experienced (CMSX-4 showing the worst severity, followed by CM247LC DS and then IN6203DS which showed no evidence of cracking at all) and the ranking appeared to be correlated to the gamma prime volume fraction. This suggests the gamma prime volume fraction is associated with the crack mechanism with lower values increasing the resistance to stress corrosion cracking. From the findings of this research, a new crack initiation/propagation mechanism is proposed which is based on a summation of stresses that includes those associated with the gamma prime.

中文翻译：

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CMSX-4、CM247LC DS 和 IN6203DS 镍基高温合金的应力腐蚀测试

应力腐蚀和热腐蚀的共同作用可能导致镍基高温合金发生应力腐蚀开裂，其机理尚不清楚。本研究的目的是通过在 550、500 和 450 °C 的温度下对 CMSX-4、CM247LC DS 和 IN6203DS 高温合金进行一系列应力腐蚀暴露来增强理解。完成暴露后，根据所经历的开裂严重程度对高温合金进行排名（CMSX-4 显示最严重的严重程度，其次是 CM247LC DS，然后是 IN6203DS，根本没有显示开裂迹象），并且排名似乎是相关的到伽马素数体积分数。这表明 gamma 素数体积分数与裂纹机制有关，较低的值会增加对应力腐蚀开裂的抵抗力。