热处理状态对GH4698合金盘件组织和蠕变性能影响研究

开展了GH4698盘件后续热处理对盘件显微组织和蠕变性能影响研究以及GH4698盘件标准热处理下750℃的全阶段蠕变行为研究。试验结果表明:GH4698盘件标准热处理后的显微组织由晶内两种尺寸的球状γ'相和碳化物组成。增加第四段热处理后,显微组织有所变化,晶内小γ'相尺寸有所增加,晶界γ'相贫化区的宽度明显减小,晶界颗粒状碳化物析出更加完善。四段热处理后对GH4698盘件在750℃/382 MPa下的蠕变极限有利。GH4698合金750℃全蠕变曲线以及俄原型机盘件蠕变性能对比表明,GH4698合金在750℃稳态蠕变阶段较短,盘锻件的显微组织和晶粒度的不均匀会造成蠕变性能较大波动,合理的蠕变性能验收条件应为700℃/412 MPa/100 h下残余应变≤0.2%。

Influence of Heat Treatment System on Microstructure and Creep Properties of GH4698 Alloy Disk

The effect of heat treatment on microstructure and creep properties of GH4698 disc and its all-phase creep behavior after standard heat treatment under 750 ℃ were studied. The results show that GH4698 plate microstructure after standard heat treatment is composed of globular gamma prime phase and carbides within grains. After the fourth stage heat treatment,the microstructure changed. Small gamma prime phase grew up,gamma prime phase dilution zone width along the grain boundary significantly reduced,and carbide precipitation along the grain boundary granular was more perfect. The fourth stage heat treatment is favorable to the creep limit at 750 ℃ /382 MPa,and the process stability is better. The complete creep curves of GH4698 alloy at 750 ℃ show that the steady-state creep stage of GH4698 alloy at 750 ℃ is relatively short. The non-uniformity of microstructure and grain size would cause greater fluctuation of the creep properties. The reasonable acceptance condition for creep properties is σp≤0. 2% at 700 ℃ /412 MPa /100h.