中文摘要：

测定了新型粉末高温合金FGH98在650 ℃空气环境中的疲劳裂纹扩展速率, 与前两代粉末高温合金FGH95和FGH96的裂纹扩展速率进行了比较分析, 研究了合金显微结构以及保载时间对FGH98合金裂纹扩展速率的影响. 结果表明, FGH98合金的高温疲劳裂纹扩展抗力较前两代粉末高温合金有了明显提高. 控制固溶后以适当的方式冷却, 使得二次和三次γ’相均匀匹配析出, 可以获得具有良好疲劳裂纹扩展抗力的合金组织. 粗晶组织有利于降低FGH98合金的疲劳裂纹扩展速率, 尤其是在近门槛区. FGH98合金的高温疲劳裂纹扩展速率随保载时间的增加而增加, 其断裂模式相应地从穿晶-沿晶混合断裂变为沿晶断裂.

英文摘要：

Powder metallurgy superalloys are important materials for manufacturing aero engine turbine disks which are subjected to loading in the forms of fatigue and creep-fatigue in service. In order to meet the increasing demands for advanced nero engines with high thrust-weight ratios, a novel generation of Ni-based powder metallurgy superalloy FGH98 was developed, which was expected to have high strength and good damage tolerance property. For the sake of examining the fatigue crack growth resistance of FGH98, the fatigue crack growth rate of this novel superalloy was investigated at 650 ~C in air and then compared with those of the first two generations of powder metallurgy superalloys FGH95 and FGH96. The effects of microstructnres and hold-time on the fatigue crack growth behavior of FGH98 were studied. It was found that the fatigue crack growth resistance of FGH98 was significantly improved in comparison with those of FGH95 and FGH96. Conducting proper cooling methods after solution could make the secondary and tertiary γ＇ phase precipitate in a uniform order, causing that the alloy could have good fatigue crack propagation resistance. It was also found that FGH98 with coarser grains showed a lower fatigue crack growth rate, especially in the near-threshold regime, and its fatigue crack growth rate increased with increasing hold-time,and correspondingly, its fracture mode changed from a mixture of transgranular-intergranular into pure intergranular.