The fatigue life and fractures of austenitic steel AISI 304 after the chemical-thermal treatment

Abstract

The service life of components is related to surface abrasion, corrosion effects, as well as the occurrence of fatigue cracks. These effects begin to spread from the surface of the components and therefore it is very important to properly influence the mechanical properties of the materials to increase the service life. In chemical-thermal treatment, the resistance of the surface layer is increased by saturating the surface of the components with suitably selected chemical elements. This affects the change in structure and mechanical properties.The article will be focused on the analysis of fatigue and fracture mechanisms of samples made of austenitic steel AISI 304, which will be subjected to a dynamic test, especially the three-point bending test. Samples for tests will be used in two states, after chemical-thermal treatment and in the initial state for comparison. Plasma nitriding will be chosen as the chemical-thermal treatment. Plasma nitriding technology has been commercially used in industrial production to improve the fatigue, anti-corrosion and tribological properties of steels.The aim of the paper is to compare the microstructural changes that took place during the nitriding process and fractographic analysis of fracture surfaces of samples that will be subjected to a three-point cyclic fatigue load. Fractography should determine the crack initiation site, the mechanism of crack formation and propagation, and the type of fracture.