The combined creep-fatigue loading tests have been carried out on SUS 316 stainless steel at 650°C. The data obtained were evaluated using the linear life fraction damage rule. The results evaluated were discussed on the basis of the observations of cracking and fracture modes.
SUS 316 stainless steel under combined creep-fatigue loadings at 650°C was ruptured by an accumulation of either creep damage or fatigue damage. The better evaluation of accumulated creep damage to rupture could be made using a term of ΣNc1εc/(Σεc)cyclic, where Nc is the number of combined creep-fatigue loading cycles to rupture, εc is the creep strain in creep loading Part of combined creep-fatigue loading test, and(Σεc)cyclic is the creep strain to fracture in cyclic creep test.
The specimens of which the rupture life was evaluated by the accumulation of fatigue damage were fractured by the growth of fatigue transgranular cracks. On the other hand, the specimens of which the rupture life was evaluated by the accumulation of creep damage were fractured by the growth and linkage of wedge-type intergranular cracks. It is suggested from discussing on the present data and the previously obtained data for SUS 304 stainless steel at 700°C that further investigation is needed concerning the correlation between creep-fatigue interaction and creep fracture characteristics.