Effect of heat treatment on tribological properties of AISI 316L manufactured through selective laser melting

Metal additive manufacturing is a demanding manufacturing technique in industrial and aerospace applications. Selective laser melting (SLM) is a metal additive manufacturing process that can produce parts with higher dimensional accuracy than conventional manufacturing processes. Metallic components produced by SLM generally require heat treatment to improve mechanical, tribological and microstructure properties. This study investigates the impact of heat treatment on SLM-manufactured stainless steel AISI 316L and its microstructure evolution, 3D wear topography, mechanical, residual stress, and tribological properties. The SLM printed as-built (AB) sample has undergone two heat treatments in a Nabertherm muffle furnace: heat treatment (HT1) at 8700 C and heat treatment (HT2) at 12000 C for 4 h of dwell time. The wear and friction tests of AISI 316L samples is optimized by Response surface methodology (RSM) with process parameters including sample condition as-built (AB), heat treatment (HT1), and heat treatment (HT2) samples of various applied loads (5 N, 10 N, and 15 N). The residual stress and microhardness before and after heat treatments were studied. The microstructural properties of as-built and heat-treated samples were investigated by the optical microscope, field emission scanning electron microscope, 3d wear track topography is used to examine the wear depth profile and its surface roughness, X-ray defragmentation analysis, and electron backscattered diffraction. Elemental composition is analyzed via Energy Dispersive X-ray Spectroscopy. The results illustrate that heat treatment does not affect phase change; only single-phase austenite is observed, the residual stress is completely removed after the heat treatment process, and the microhardness decreases with increasing heat treatment temperatures. The heat treatment can decrease microhardness and wear resistance; wear oxide debris is formed after wear and friction testing. The coefficient of friction (COF) increases due to heat treatment and reduction in microhardness. After heat treatment the crystallographic orientations in grain growth, grain orientation is entirely refined, austenitic twin boundaries are increased after heat treatment.