Abstract: Research is made on the evolutions of microstructure and fatigue life of TP347H stainless steel under pure fatigue(PF) and creep-fatigue(CF) at 550 ℃.The fracture morphology of scanning electron microscope(SEM) indicates that high temperature dynamic recovery existed under the interactions of creep and fatigue, on the creep-fatigue fracture no secondary cracks and cleavage planes are formed, but on pure fatigue fracture many secondary cracks and small cleavage planes exist; Transmission electron microscope(TEM) morphology indicates that distinct dislocation walls and dislocation cells are formed on local positions under the interactions of creep and fatigue, dislocation multiplication density decreases significantly relative to under pure fatigue. The cyclic softening of TP347H is very obvious and leads to the obvious reduction of fatigue life under interactions of creep and fatigue. Creep-fatigue experiments under various strain amplitude of TP347H prove that creep-fatigue life are reduced obviously relative to pure fatigue, the reduced degree increases with the increment of strain amplitude.

Key words: creep, fatigue, high temperature, interactions, TP347H