Fatigue fracture characteristics of GH4169 super-alloy under non-proportional loading at high temperature

Biaxial fatigue fracture feature of GH4169 super-alloy under the total strain amplitude control of in-phase (IP) loading and out-of-phase (OP) loading with phase angles of 45° and 90° at 650° was studied. The results indicate that cracks homogenously initiate on the surface of the samples under in-phase loading while the number of crack initiation decreases with the increase of non-proportional loading. The fatigue fracture exhibits apparently tear ridge in the radial direction under in-phase loading, however, there are tear planes with non-proportional loading. At the phase angle of 90°, the fatigue fracture shows the feature of all tear planes, which appears in the circumferential direction. On the boundary of two crack propagations the fatigue striations were found along the radial direction. At the instantaneous fracture area the depth of dimples became larger with the increase of non-proportional loading.