High cycle fatigue of superalloy single crystals at high mean stress

Single crystals of CM186SC superalloy with 〈0 0 1〉 orientation were subjected to creep and creep/fatigue loading at a temperature of 850 °C. Time to creep fracture of notched specimens was found to be higher than that of smooth specimens for the same net stress. Superposition of a cyclic stress component on the static stress component leads to the formation of persistent slip bands running through the γ matrix and the γ′ precipitates both in the dendritic and eutectic regions and to a shortening of the lifetime at higher stress amplitudes. CM186SC crystals exhibit a lower resistance against creep and creep/fatigue loading than CMSX-4 crystals.