Creep property measurement of service-exposed SUS 316 austenitic stainless steel by the small-punch creep-testing technique

The creep properties for SUS 316 HTB austenitic stainless steel were evaluated by using the small-punch creep test at 650°C for loads of 234, 286, 338, 408, and 478 N and at 700°C for loads of 199 and 234 N. The creep curves, determined by means of the small-punch creep test, were similar to those obtained from a conventional uniaxial creep test. That is, they exhibited clearly the three creep stages. The width of secondary creep stage and rupture time t_r decreased with the increase in testing load level. The creep rupture strength for the service-exposed material was lower than that of the as-received material at high testing loads. However, the creep resistance behavior was opposite at relatively low load levels. This difference in creep resistance was explained on the basis of the difference in the creep deformation and microstructural evolution during tests. It was also found that the ratio between the load of small-punch creep test and the stress of uniaxial creep test was about 1 for having the same value of creep rupture life.