SMALL PUNCH CREEP TEST OF SERVICE-EXPOSED SUS 316 HTB SUPERHEATER TUBES OF FOSSIL BOILERS

摘要

The creep properties were evaluated in a SUS 316 HTB austenitic stainless steel by using the small-punch creep test. The applied loads were 234, 286, 338, 408 and 478 N at 650°C, and 199 and 234 N at 700°C. The creep curves 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. While, the creep resistance behavior was opposite at relatively low load levels. This difference in creep resistance was explained based on the difference in the creep deformation and/or fracture mechanism.