High-Cycle Fatigue Properties of Austenitic Stainless Steels with Different Nitrogen Content.

Abstract

The fatigue properties of austenitic stainless steels with different nitrogen content have been investigated in the high-cycles region using Ono-type rotating bending fatigue testing machine. The materials used in this test were three kinds of austenitic stainless steels, i.e. typical austenitic stainless steel, SUS 304 and nitrogen-contained SUS 304 (SUS 304 N and YUS 170). When considering the fatigue limit is the maximum stress amplitude by 1×107 cycles, the fatigue limit of SUS 304 N becomes remarkably larger than that of SUS 304, while the fatigue limit of YUS 170 is smaller than that of SUS 304 irrespective of higher nitrogen content in YUS 170. The above difference would be caused by the difference of the effect of strain aging and deformation induced martensite transformation, because YUS 170 has more stable austenitic structure than SUS 304 according to higher nitrogen content. In addition, the non-propagating micro-cracks have not been observed in the not-broken specimens of SUS 304 and SUS 304 N subjected to the stress amplitude of fatigue limit by 1×107 cycles. While a few micro-cracks were observed in the specimen of YUS 170 under same condition as the above and these specimens were broken under the following same stress amplitude by 1.2×107 cycles.