High temperatuer low cycle fatigue of DZ40M cobalt-base superalloy

Stress controlled low cycle fatigue tests on directionally solidified cobalt- base superalloy DZ40M have been conducted at 900°C in ambient atmosphere. DZ40M superalloy exhibits high low cycle fatigue resistance. The fractography observation indicates that preferentially oxidized carbides at specimen surface act as crack initiation sites, and carbides in matrix have the retardation effect on crack propagation. Oxdation effect reduces alloy ductility, that promotes crack propagation. High temperature low cycle fatigue damage of DZ40M superalloy results from the interaction of thermo-mechanical fatigue and enviromental oxidation.