Microstructure and stress-rupture life of high W-content cast Ni-based superalloy after 1000–1100 °C thermal exposures
Microstructure and stress-rupture life of high W-content cast Ni-based superalloy after 1000–1100 °C thermal exposures
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DOI：
10.1016/j.msea.2018.04.037
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发表时间：
2018-05
期刊：
影响因子：
6.4
通讯作者：
Zhou Tongjin;H. Ding;Xiuping Ma;W. Feng;Huibin Zhao;Meng Yu;Huaxia Zhang;Yongmin Lv
中科院分区：
文献类型：
--
作者：
Zhou Tongjin;H. Ding;Xiuping Ma;W. Feng;Huibin Zhao;Meng Yu;Huaxia Zhang;Yongmin Lv
研究了可用作1050 °C以上等温锻造模具材料的高W铸造镍基高温合金。根据显微组织的演变，在1100 °C/70 Mpa下测试了合金的持久寿命，并分别在1000、1050和1100 °C热暴露100-1000 h后对合金进行了评估。结果表明，随着暴露温度的升高，γ析出物的粗化和聚集随着其体积分数的降低而降低，在1100 °C时尤为明显。γ析出物的粗化速率随暴露温度的升高而增加，随后是修正的LifshitzSlyosvWagner成熟理论。在1000、1050和1100 °C下的粗化速率系数(K)分别为5.72、7.40和8.71 nm/s1/3。此外，在这些温度下，它发现枝晶间区域中的块状M6C碳化物析出并粗化。此外，M6C碳化物相互连接，就像一条缠绕在晶界和沿共晶γ‘相的链条。热暴露后，由于组织的退化，持久寿命从94.8 h下降到49.3 h，1100 °C，1000 °C，1000 h。最后，结合实验结果，详细讨论了组织演变与持久寿命的关系。
High W-content cast Ni-based superalloy which can be served as isothermal forging die materials over 1050 °C was investigated in this paper. Based on the microstructure evolutions, stress-rupture life of the alloy were examined under 1100 °C /70 MPa, where the alloy was evaluated after thermally exposed at 1000, 1050, and 1100 °C for 100–1000 h, respectively. Results showed that increasing of exposure temperature can cause coarsening and coalescing of γ′ precipitates along with a decreasing in their volume fraction, especially at 1100 °C. The coarsening rate of the γ′ precipitates increased with the exposure temperature and followed by the modified Lifshitz-Slyozov-Wagner coarsening theory of Ostwald ripening. The coarsening rate coefficient (k) at 1000, 1050, and 1100 °C was calculated to be 5.72, 7.40, and 8.71 nm/s1/3, respectively. In addition, at those temperatures, it found the blocky M6C carbides in the interdendritic area to be precipitated and coarsened. Furthermore, the M6C carbides linked with each other like a chain wrapped around the grain boundary and along the eutectic γ′ phase. Because of the degradation of the microstructure, the stress-rupture life decreased after thermal exposure, from 94.8 h at 1000 °C to 49.3 h at 1100 °C for 1000 h. Finally, in view of the experimental results, a relationship between the microstructural evolution and the stress-rupture life of the alloy was discussed in details.