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利用真空冶炼制备了不同(W+Mo)/Cr比(质量比)的铸造镍基高温合金,采用OM,SEM和TEM观察了合金试样的微观组织,研究了(W+Mo)/Cr比对合金组织演化和持久性能的影响.结果表明,(W+Mo)/Cr比对热处理态组织无明显影响,主要组成相为g基体、g’相、初生MC和晶界二次碳化物.长期时效期间,合金试样的组织演化主要包括g’相粗化、拓扑密排相(TCP)相析出、MC分解和晶界粗化.随(W+Mo)/Cr比降低,MC的热稳定性明显降低,晶界粗化程度升高,晶界碳化物发生了M6C→M6C+M23C6→M23C6的转变.同时,TCP相的析出量明显减少.当(W+Mo)/Cr比为0.22时,无TCP相析出.另外,(W+Mo)/Cr比由高于0.55降低至0.37时,TCP相的种类由m相转变为了m与s相共存.g’相和晶界粗化及TCP相的析出是引起合金持久性能降低的主要原因.综合(W+Mo)/Cr比对合组织演化和持久性能的影响得出,(W+Mo)/Cr比约为0.37时,合金具有最佳的持久性能.
The cast Ni-base superalloys with different (W + Mo) / Cr ratios (mass ratios) were prepared by vacuum smelting. The microstructures of the alloy samples were observed by OM, SEM and TEM. The effects of (W + Mo) (W + Mo) / Cr ratio has no significant effect on the microstructure of the heat-treated state, and the main components are g matrix, g ’phase, primary MC and grain boundary secondary carbides. During the long-term aging, the microstructure evolution of the alloy samples mainly includes g ’phase coarsening, top-dense phase (TCP) phase precipitation, MC decomposition and grain boundary coarsening. As the ratio of (W + Mo) / Cr decreases, While the grain boundary carburization increased, the transformation of M6C → M6C + M23C6 → M23C6 occurred in the grain boundary carbides, and the precipitation of TCP phase decreased obviously.When the ratio of (W + Mo) / Cr was 0.22 , No TCP phase was precipitated, and when the ratio of (W + Mo) / Cr decreased from 0.55 to 0.37, the type of TCP phase changed from m phase to m and s phase coexisted. The precipitation of TCP phase is the main reason for the decrease of the ductility of the alloy. The effect of the combination of (W + Mo) / Cr ratio on the microstructure evolution and ductility results in (W + Mo) / Cr ratio of about 0.37. Best lasting performance.