Influence of hot isostatic pressing on fatigue performance of K403 nickel-based superalloy

Low cycle fatigue experiments of K403 Nickel-based superalloy miniature specimens were carried out in the high temperature fatigue testing machine at 750 °C. These specimens were cut from turbine blades which were processed with hot isostatic pressing (HIP) under two different stresses, 135 MPa and 145 MPa, respectively. The geometric model of the K403 alloy was established based on the observation of its microscopic structure under the scanning electron microscopy (SEM), while its constitutive model was built based on the crystal plasticity theory. Both the fatigue experiments and the finite element analysis (FEA) indicated that the HIP process (especially 145 Mpa HIP treatment) could dramatically reduce the stress concentration and plastic deformation of K403 alloy by eliminating the internal casting defects effectively so as to extend its fatigue life at 750 °C. The SEM analysis demonstrated that the grain boundary carbides have been gradually refined. Moreover, the microstructure of γ and γ′ phase could be largely optimized, which guarantees the improvement of the alloy fatigue property.