The evolution and healing process of creep-fatigue damage are discussed on the basis of the experimental observation of cavities and small cracks. Multiple cavities and small cracks are formed along grain boundaries inside a smooth specimen of a Cr-Mo-V steel in creep-fatigue with slow-tension and fast-compression cycling at the relatively high temperature of 923 K. The cracks begin to appear at the middle stage of life, while the cavities initiate in the very early stage. The failure is brought about by the coalescence of cracks in the late stage. It is also found that these cavities and cracks caused by the diffusive creep in tension disappear during successive compression creep in creep-fatigue with fast-tension and slow-compression cycling. The failure life of the specimen can be extended by the healing cavities and cracks.
