FGH95粉末冶金高温合金长期时效的组织稳定性

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500～5000h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1～3μm的γ′相,呈不规则块状在晶界析出;尺寸约为500nm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60～200nm范围内变化。合金时效3000h时发现晶界上生成M23C6型碳化物。

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

The microstructure of a Ni-based P/M superalloy FGH95 after long-term aging at 650 ℃ 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 ℃.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.