Investigation of properties of ion-nitrided AISI 304 austenitic-stainless steel

Purpose - The aim is to provide detailed mechanical and metallurgical examinations of ion-nitrided austenitic-stainless steels. Design/methodology/approach - Austenitic-stainless steel was the material chosen for the present study. Ion nitriding process was applied to fatigue and tensile samples prepared by machining. Process temperature was 550 degrees C and treatment time period 24 and 60 h. Then, tensile, fatigue, notch-impact, hardness tests were applied and metallographic examinations were performed. Findings - High temperature and longer treatment by ion nitriding decreased fatigue and tensile strengths together with notch-impact toughness. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis revealed formation of nitrides on the sample surfaces. Surface hardness increased with an increase in process time due to diffusion of nitrogen during ion nitriding. Research limitations/implications - It would be interesting to search the different temperature and time intervals of the ion nitriding. It could be a good idea if future work could be concentrated on ion nitriding on welded stainless steels. Practical implications - Surfaces of mechanical parts are exposed to higher stress and abrasive forces compared to inside mechanical parts during the time period that mechanical components carry out their expected functions. When stresses and forces exceed the surface strength limit of the material, cracks begin to form at the material surface leading to abrasion and corrosion. Therefore, surface strength of materials needs to be increased to provide a longer service life. Ion (plasma) nitriding is a possible remedy for surface wear. Originality/value - The main value of this paper is to contribute and fulfil the detailed mechanical and metallurgical examinations of ion-nitrided austenitic-stainless steels that are being studied so far in the literature.