Giga-cycle Fatigue of AISI 316L After Sensitising of Structure

Giga-cycle fatigue (107 ˂ N ˂ 1010 cycles) is subject of interest of the most important research centres in the world. This interest is involved by existing fatigue fractures of real mechanical parts after more than billions cycles and with growing demands on reliability and safety of structural components. Stainless austenitic steels are used in transport devices which are operated for long time at high temperatures. During operation at higher temperatures in these steels can occur microstructural changes, as result of sensitisation which can cause embrittlement. Authors present their own experimental results about fatigue resistance of sensitised austenitic stainless steel AISI 316L in the very high cycle region (N = 2×106 ÷ N = 5×109 cycles). Fatigue tests were carried out on the ultrasonic fatigue testing machine (f = 20 kHz) with symmetrical push-pull loading (R = -1) and at temperature 20±5 °C. In the very high cycle region was observed continuous decrease of fatigue strength and there was no effect of sensitisation recorded on the fatigue properties.