Low Cycle Fatigue Properties of FGH97 P/M Superalloy with Different Test Control Modes

An FGH97 superalloy disc was manufactured by argon atomization (AA) + hot isostatic pressing (HIP) + heat treatment process. Then the microstructure at different positions, the tensile properties at 650 degrees C, the low cycle fatigue properties with stress and strain constant-amplitude controlling, and the fatigue fracture of the samples were investigated. The results reveal that the grains size and the size and morphology of the gamma' are similar at different positions. The tensile strength at 650 degrees C is between 1325 and 1340 MPa, and the yield strength is between 1010 to 1025 MPa, which are relatively stable. The average N-f of stress-controlling is 200 000 cycles at different positions, and Weibull distribution eta is 215 194. The effect of the inclusion of less than 80 mu m in size on N-f is not obvious. The Weibull distribution eta of strain-controlling is 14 622 when the N-f is less than 20 000 cycles, and 44 342 when N-f is more than 20 000 cycles. The variation of inclusion area leads to the difference of characteristic value beta of N-f Weibull distribution. The crack source of fatigue fracture is mainly the inclusions, and the fracture morphology is rather similar. The fatigue of the strain controlling is more sensitive to the inclusions.