FGH95粉末冶金高温合金长期时效的组织稳定性

Microstructure Stability of FGH95 P/M Superalloy after Long-Term Aging

摘要:

利用扫描电镜和透射电镜观察了FGH95镍基粉末冶金高温合金在650 ℃长期时效后的显微结构，评价了该合金在时效过程中的组织稳定性。结果表明，该合金在650 ℃具有较好的组织稳定性。经500~5000 h时效后，合金的主要析出相为γ′相、MC型和M23C6型碳化物，在合金中没有发现TCP相。γ′相在不同热处理时期具有3种不同的尺寸及形貌：尺寸为1~3 μm的γ′相，呈不规则块状在晶界析出；尺寸约为500 nm的γ′相，呈蝶形均匀分布于基体中，随时效时间延长，其大小、形貌及在基体中的分布稍有变化；更小的γ′相在长期时效过程中经历不规则长大、分裂、再长大和再分裂的循环过程，尺寸在60~200 nm范围内变化。合金时效3000 h时发现晶界上生成M23C6型碳化物。

Abstract:

The microstructure of a Ni-based P/M superalloy FGH95 after long-term aging at 650 oC was observed by SEM and TEM and its microstructure stability was also investigated. The results show that the microstructure of the alloy is stable at 650 oC. The major precipitated phases of the alloy are γ′ phase and carbides of MC and M23C6 without TCP phase precipitating after aging for 500-5000 h. The γ′ phase is precipitated in the matrix in three kinds of sizes during different heat treatment processes. The size of bulk γ′ phase is about 1 to 3 μm, which is precipitated on grain boundary. The size of intragranular γ′ phase is about 500 nm, with the shape of butterfly, which changes a little in size, morphology and distribution in matrix during the aging process. And the smaller γ′ phase experiences a series of changes such as growing up, splitting and growing up again and splitting again in long-term aging. Its size is in a range of 60 to 200 nm. A kind of carbide M23C6 is found on the grain boundary in the alloy aged for 3000 h.