多步热处理对GH4742合金组织性能的影响

Effect of multi-stage heat treatment on microstructure and properties of GH4742 alloy

采用多步热处理,研究了不同固溶温度和高温时效温度对GH4742高温合金组织性能的影响。结果表明,固溶温度显著改变晶粒尺寸和一次γ′相形态。固溶温度为1090℃时,基体中存在大量未溶的一次γ′相,可以有效阻止晶粒长大,同时这种粗大γ′相以及后续时效过程中形成的细小γ′相共存的组织使得合金具有良好的综合力学性能。高温时效处理对组织形貌影响较小,但可以改变γ′相的尺寸,显著影响晶界碳化物的形态,通过Mo置换一次碳化物MC中的Nb、Ti,使晶界连续分布的碳化物发生溶解形成颗粒状的碳化物,显著降低了GH4742高温合金的高温持久性能。

Effects of different solution temperature and high aging temperature on microstructure and mechanical properties of GH4742 superalloy were studied by multi-stage heat treatment.The results show that the grain size and primaryγ′phase morphology can be significantly influenced by adjusting solution temperature.When the solution temperature is 1090℃,there are a large amount of undissolved primaryγ′phases in the matrix,which can effectively prevent the growth of grains,and the coexistence of those coarse primaryγ′phase and fineγ′phase formed in the subsequent aging process makes the alloy achieves an excellent comprehensive mechanical properties.High temperature aging treatment has little effect on microstructure,but it can change the size of theγ′phase and obviously affects the morphology of carbides on the grain boundary.By replacing Nb and Ti in the primary carbide MC with Mo,the carbides continuously distributed on the grain boundaries are dissolved to form granular carbides,which significantly reduces the high temperature durability of the GH4742 superalloy.