TP347H的高温蠕变-疲劳交互规律

Interactions Between Creep and Fatigue of TP347H under High Temperature

对TP347H不锈钢进在550℃下纯疲劳及550℃下的蠕变-疲劳交互下的微观组织演化及疲劳寿命变化进行研究。断口的扫描电镜形貌表明在蠕变-疲劳交互下存在高温动态回复,使得蠕变-疲劳断口未形成二次裂纹与解理面,而在纯疲劳下存在较多二次裂纹与解理面;透射电镜形貌表明在蠕变疲劳交互下金属内部局部会形成清晰的位错墙和位错胞结构,错增殖密度相对于纯疲劳也大大降低,此时材料的循环软化特征明显,因此蠕变-疲劳交互会导致材料的疲劳寿命显著降低。对不同应变幅下TP347H的蠕变-疲劳寿命试验证明不同应变幅下TP347不锈钢的蠕变-疲劳循环寿命相对于纯疲劳条件下都有降低,降低的程度随应变幅的增加而增大。

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 ofscanning 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.