Exploration on the fatigue behavior of low-temperature carburized 316L austenitic stainless steel at elevated temperature

Abstract

The fatigue behavior of low-temperature carburized 316L austenitic stainless steel at elevated temperature was investigated. Uniaxial tensile tests and rotating bending fatigue tests were performed on untreated and carburized 316L austenitic stainless steel at 300 °C, 400 °C, 500 °C and ambient temperature. Results show that carburized case can improve the fatigue strength at both ambient and elevated temperatures significantly. The improvements of tensile strength and endurance limit by carburized case at elevated temperature are even higher than those at ambient temperature. Moreover, the higher improvement of fatigue performance at elevated temperature is mainly due to the better strengthening effect of carburized case on the strength, the brittleness reduction and the redistributions of carbon content of carburized case. Based on the observation of fracture morphologies, fatigue fracture mechanisms of untreated and carburized specimens at different temperatures were analyzed. For untreated specimens, fatigue cracks always initiate from the surface at both ambient and elevated temperatures. For carburized specimens, fatigue cracks initiate at subsurface near the boundary between carburized case and substrate at ambient temperature. At elevated temperature, fatigue cracks initiate near the boundary under the high applied stress while under low applied stress, fatigue cracks initiate from the inclusions.