Prestrain effects on creep ductility of a 316 stainless steel light forging

Specimens were machined from a section of 316 stainless steel header which was in service for approximately 30 000 h. Constant stress creep tests were performed at 450 MPa and 575 degrees C on materials subjected to various l evels of prestrain to determine the effect of prior deformation on subseque nt creep behaviour. The results show that, provided the prestrain exceeds t he initial strain on loading to the creep test conditions in the un-prestra ined condition, a significant reduction in rupture life, minimum creep rate and creep ductility was obtained by increasing prestrain. The Monkman-Gran t relationship proved to be a reliable indicator of the effect of prestrain on creep properties and showed that the reduced rupture lives were a conse quence of the progressive exhaustion of creep ductility with prestrain. (C) 1999 Elsevier Science Ltd. All rights reserved.