Improved tribological performance of AISI 316L stainless steel by a combined surface treatment: Surface texturing by selective laser melting and plasma nitriding

Surface texturing, which depends on the formation of different patterns on materials, is used to improve the tribological performance of materials. Therefore, the effects of different surface textures fabricated by selective laser melting (SLM) and plasma nitriding on the friction and wear properties of AISI 316L stainless steel were investigated in this study. AISI 316L samples with hexagonal, random, ellipse, triangle, square and the new model (ellipse+triangle) surface textures (patterns) were produced by SLM and they were plasma nitrided at 400 °C for 2 h. Tribological behavior of them was determined by a pin-on-disc type tribo-tester under dry and simulated body fluid (SBF) conditions. XRD, SEM, microhardness tester and 3D surface profilometer were used for characterizations. The results showed that the surface textures and their area density were highly effective on the friction and wear properties and the increasing area density provided better wear resistance. Ellipse geometric pattern had the lowest friction coefficient and wear rate because it trapped wear debris and provided a smooth stress transition in comparison to the sharp-edged textures by enabling hydrodynamic benefit. Plasma nitriding led to decrease friction coefficient and wear rate for all surface textures since it produced a hard compound layer. Also, the best results were obtained from SBF because solid-solid contact was prevented and wear debris was removed by solution.