Thermal-Mechanical Fatigue and Isothermal Low Cycle Fatigue Fracture Behavior of Powder Metallurgy Superalloy FGH95

High temperature low cycle fatigue behavior of Powder Metallurgy superalloy FGH95 was studied.A basic triangular cycle with a constant temperature of 600℃ and an inphase triangular cycle with maximum and minimum temperature of 350℃ and 600℃ respectively were used for thermal-mechanical fatigue testing.The strain ratio of minimum to maximum strain is -1.0.The influence of the above two loading cycle on cyclic stress response behavior,mechanism of fracture at high temperature and fatigue life was investigated.At same strain amplitude,it was found that the TMF life of in-phase loading form is shorter than that of isothermal low cycle fatigue loading form.High temperature low cycle fatigue behavior of PM superalloy FGH95 depends not only on loading form,but also on magnitude of stain.The microstructure damage behavior of high temperature low cycle fatigue is discussed.The results show that fatigue,creep and oxidation damage always develops simultaneously during low cycle fatigue at high temperature.Fracture is mainly intergranular and transgranular under inphase thermal-mechanical fatigue. The path of crack initiation and growth is transgranular under conditions of isothermal low cycle fatigue.