Influence of grain size and ?-phase stability on the fatigue limit of high-strength austenitic steels

Abstract

1. The high fatigue strength of N26KhT1 metastable austenitic steel is caused not only by strengthening as a result of phase strain hardening and aging but also by the instability of the Fe−Ni−Ti austenite. 2. An increase in grain size leads to a reduction in the fatigue limit of N26KhT1 and 40G18Yu3F steels. The fatigue limit of 40G18Yu3F stable dispersion hardening steel is more sensitive to a change in grain size. 3. The straight-line relationship of the fatigue strength of N26KhT1 and 40G18Yu3F steels to grain size, described by the Hall-Petch equation, has a break, which is caused by a change in the character of failure in the transition from the fine- to the coarse-grained condition of the steel. 4. The low-cycle fatigue strength of N26KhT1 steel is practically independent of grain size.