Time- and cycle-dependent crack propagation in Haynes 282

Haynes 282 is a promising superalloy candidate for several high-temperature applications in both aero and land-based gas turbine engines. To study the crack growth behaviour under time-dependent conditions relevant to such applications, a test program was carried out at room temperature up to 700 \ub0C with conditions ranging from pure cyclic to sustained tensile loading. At 650 \ub0C and high stress intensity factors the crack growth was fully time-dependent for dwell-times of 90 s and longer. At lower stress intensities, the behaviour was mainly controlled by the cyclic loading, even under dwell conditions. The behaviour under dwell-fatigue conditions was well described by a liner superposition model. The main crack growth occurred transgranularly at room temperature and there was a transition in cracking behaviour from cycle dependent transgranular growth to time-dependent intergranular propagation at dK=45 MPa m^0.5 for the high temperature tests. No effect of cyclic frequency could be observed at room temperature, and at lower frequencies the crack growth rate increased with temperature