Life extension by cavity annihilation heat treatment in AISI 316 stainlesssteel under creep-fatigue interaction conditions

The creep-fatigue life extension of AISI 316 austenitic stainless steel by heat treatment for cavity annihilation was investigated. Different heat tre atments were conducted to find better conditions which could enhance the ef fect of treatments for the life extension. Cavities formed during creep-fat igue tests were found to be annihilated during solution heat treatment, and the cavity annihilation led the materials to have longer creep-fatigue liv es. Having different heat treatments, it can also be suggested that the ext ension of the creep-fatigue life can be maximized by changing the ageing co ndition, after solution treatment, to have the lower density of grain bound ary carbides that serve as nucleation sites for the cavities. The specimen aged at a higher temperature which has the lower value of cavity nucleation factor, P', has a longer extended creep-fatigue life. In this specimen, ca vity re-generation during the loading after annihilation of previous caviti es is retarded owing to the lower density of the grain boundary carbide. (C ) 2000 Kluwer Academic Publishers.