Tensile and low cycle fatigue properties of nickel-base powder metallurgy superalloy FGH95

The tensile behavior of a nickel-base powder metallurgy (PM) FGH95 superalloy was studied in the temperature range from 420°C to 650°C with strain rate from 0.0001 s^-1 to 0.01 s^-1. The low cycle fatigue (LCF) behavior of this superalloy was investigated in the temperature range from 420°C to 650°C under push-pull mode (R=-1) and pull mode (R=0) at strain rate of 0.001 s^-1. The results of tensile testing show that the effect of strain rate on the Young's modulus, tensile yield strength, and plastic modulus can be neglected in the experimental temperature range. And the influence of temperature on the Young's modulus, tensile yield strength, and plastic modulus is not obvious in the strain rate range from 0.0001 s^-1 to 0.01 s^-1. The PM FGH95 is sensitive to the micro-defect, which has a significant deleterious effect on FGH95 material mechanical behavior. The results of LCF reveal that the PM FGH95 is the cyclic hardening material. For mode R=-1, the effect of temperature on LCF life can be neglected; but for mode R=0, the temperature has profound influence on the LCF life. At this case, the LCF life decreases drastically with the temperature increasing. The SEM investigation of LCF specimens shows that there are a lot of cleavages on fracture surface, fatigue striations are absent, and this fracture mode may not involve significant plastic deformation. So the LCF life of PM FGH95 is almost determined by the crack initiation stage.