涡轮叶片材料CMSX-4超温状态组织演变研究

Microstructure Evolution of Turbine Blade Material CMSX-4 Under Overtemperature Condition

以涡轮叶片用材料CMSX-4合金为研究对象,采用体式显微镜、扫描电镜、维氏硬度计等研究了CMSX-4合金在超温状态下的组织演变以及硬度变化。结果表明:随温度升高,γ′相长大聚集的同时伴随着γ′相回溶,γ′相立方度下降,γ通道变宽。当超温处理温度到达1250℃时,γ/γ′相界面呈锯齿状;当温度达到1300℃后,γ′相全部回溶;当温度达到1350℃时,合金开始初熔,出现大量孔洞与γ+γ′共晶。当在1300℃以下一定温度保温时,随着保温时间的延长,γ′相百分含量逐渐减少并趋于稳定。当温度达到γ′相全部回溶温度时,因重新析出细小的二次γ′相,合金硬度显著升高,最高硬度达458 HV,比原始状态提高约12%。因此,对于过热等异常服役引起组织损伤与退化,可结合叶片宏观形貌、γ′相形态与百分含量、硬度退化情况进行材料损伤程度的评估。

This article takes the CMSX-4 alloy,which is used for turbine blades,as the research object.The microstructure evolution and hardness changes of CMSX-4 alloy under overtemperature conditions were studied using the stereomicroscope,scanning electron microscopy,Vickers hardness tester,etc.The results show that as the temperature increased,theγ′phase grew and accumulated,and resolve at the same time,while theγ′phase cubic degree decreased,and theγchannel widened.When the overtemperature treatment temperature reached 1250℃,γ/γ′phase interface became serrated.When the temperature reached 1300℃,theγ'phases were all redissolved.When the temperature reached 1350℃,the alloy began to melt,resulting in a large number of holes andγ+γ′eutectics.When holding at a certain temperature below 1300℃,with the extension of holding time,the percentage ofγ′phase gradually decreased and tended to be stable.When the temperature reached the re-dissolution temperature of theγ′phase,the hardness of the specimen increases significantly due to the re-precipitation of small secondaryγ′phase,and the highest hardness reached 458 HV,which is about 12%higher than that of the original state.Therefore,for the microstructure damage and degradation caused by abnormal service such as overheating,the damage degree of the material can be evaluated by combining the macro morphology of the blades,morphology and percentage content of theγ′phase,and hardness degradation.