Small crack propagation and closure behaviours and mechanisms in a powder metallurgy superalloy at high temperature in air

To investigate small crack propagation and closure mechanisms in a powder metallurgy superalloy FGH4096 at room and high (600 °C) temperatures in air, meso-scale digital image correlation (DIC) was applied. CODs of small cracks did not increase monotonically as cracks propagated, which was related to the potential role of subsurface crack morphology. Roughness induced crack closure was found to be the leading mechanism at times. Oxidation induced crack closure was negligible at 600 °C, resulting from the oxidation-resistance of FGH4096. Crack opening stress intensity factors were generally higher at 600 °C, which ascribed to the higher level of plasticity induced crack closure.