Influence of structure sensitising of the AlSi 316Ti austenitic stainless steel on the ultra-high cycle fatigue properties

Austenitic stainless steels are the wide-spread materials, used mainly in the power industry. In that kind of engineering application, structural parts of rotating elements reach during their lifetime very high numbers of loading cycles, exceeding 107 numbers of cycles. With regard to this fact, the data of ultra-high cycle fatigue properties are needed to be used in the qualified design. Increasing demands on the efficiency cause the increase of the operating temperature, and exposition of these materials to the elevated temperatures can cause some important structural changes, which result in the sensitising of the structure. In this study authors present their own experimental results about fatigue properties of AISI 316Ti austenitic stainless steel after sensitising, in the ultra-high cycle region (Nf = 106 ~ Nf = 3×109 cycles). Fatigue tests were carried out using ultrasonic fatigue testing device with frequency f = 20 kHz at the coefficient of cycle asymmetry R = -1, and temperature T = 20±5°C. In the ultra-high cycle region was observed the continuous decrease of the fatigue properties of the AISI 316Ti, and there was recorded the negative effect of the sensitising on the ultra-high cycle fatigue properties of the AISI 316Ti.