Creep-Fatigue-Oxidation Interactions on the High Temperature Low-Cycle Fatigue Damage of Austenitic Stainless Steels: Past, Current and Future

Abstract

Elevated temperature fatigue is a complex problem which involves a large number of additionnai factors, such as strain-rate or frequency, waveform signal, hold time and environment. Moreover most of the structural materials are metallurgically unstable when tested at elevated temperature. Empirical testing for the effect of test parameters is at a disadvantage. Concepts are needed, based on the knowledge of micromechanisms operating in elevated temperature fatigue. Although the development of our knowledge in this field is still limited, many studies have shown that a certain rationalisation can be made when the character of fatigue cracking modes, that is transgranular or intergranular, is considered. In this paper an attempt is made to review the low-cycle fatigue behaviour of austenitic stainless steels, such as 304 and 316, which are largely used in a number of components. The paper is divided into two main parts. The first part deals with transgranular fatigue at high temperature, while the second one is devoted to oxidation-creep-fatigue interactions leading to intergranular fracture. In both cases we concentrate essentially on crack initiation phenomenon.