Assessment of gas and salt bath nitriding process on AISI 304SS under dry sliding conditions
摘要
The current work examines the surface modification and improvement of tribological performance of AISI-304 stainless steel via gas and salt bath nitriding under dry sliding conditions. Although austenitic types of stainless steels have good resistance to corrosion, their surface hardness is relatively low and they have poor wear properties, thereby they are undergone with surface engineering techniques. Nitriding by gas is done for 6 h, 12 h, 18 h and salt bath treatment is done for 1 h, 2 h, 3 hrs to a temperature of 550 °C to 570 °C. Their effect on the hardness, case depth and resistance to wear is determined. SEM microstructural analysis, hardness and wear test under a load of 10 N at a speed of 1000 rpm were undergone for this experimental work. The outcomes proved the rise in hardness from 219 Hv (untreated) to 245 Hv after 3 hours of salt bath nitirding, 284 Hv after 18 h of gas nitriding with a corresponding loss in wear between 6.812 mm3 and 1.721 mm3. It was found that diffusion layer increases with the temperature and time, proving the enrichment of nitrogen and the appearance of nitrides. The experiment finds that gas nitriding at 570o C in 18 h offers the best surface qualities whereby a thick and uniform layer of nitride was formed that increases wear resistance and surface hardness significantly without loss of structural integrity.