FGH95粉末盘材料热/机械疲劳和等温低周疲劳断裂行为研究

对粉末冶金盘材料 FGH95进行了同相位 ,温度循环为 3 5 0℃到 60 0℃的热 /机械疲劳试验和 60 0℃的等温低周疲劳试验。考察了两种载荷波形下材料的循环应力响应行为和高温疲劳断裂机理以及载荷波形对疲劳寿命的影响。研究结果表明 :同相位热 /机械疲劳寿命比上限温度的等温低周疲劳寿命短。该材料在高温应变疲劳的循环应力响应行为与应变水平的大小以及循环载荷波形有关。试样的微观断口分析显示了在高温应变疲劳试验中同时存在疲劳、蠕变和氧化损伤。在同相位热 /机械疲劳载荷下 ,穿晶 +沿晶断裂为疲劳断裂的主要特征 ;在等温低周疲劳载荷下 ,裂纹主要为穿晶萌生与扩展 

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.