The Hydrodynamic Lubrication Performance of Protruded Surface Microtexturing Fabricated by Selective Laser Melting Ink-Printed Copper Nanoparticles

Surface texture is a valid way of improving hydrodynamic lubrication performance and reducing friction. In this work, a novel micro-additive manufacturing technique, selective laser melting ink-printed (SLM-IP) copper (Cu) nanoparticles (NPs) method, was developed to fabricate Cu protruded microtextures on stainless steel surface. The physical effects of texture geometry parameters on the hydrodynamic lubrication performance were investigated by theoretical calculation and experiments. The theoretical results indicated that the triangle-shaped microtexture exhibited better hydrodynamic effects compared to circular and square-shaped ones. The use of a complicated ring structure resulted in a noticeable increase in hydrodynamic pressure. For each individual shape, the friction coefficient was measured and calculated as a function of texture area or radius ratio. The experimental results, supported by the theoretical analysis, provides evidence that the protruded surface microtexture fabricated by SLM-IP Cu NPs helped improve the tribological performance. The geometric parameters of the protruded microtexture’s size should be taken into account for the optimum size of texture structure. Furthermore, the operating condition of the protruded surface texture were evaluated. A transition point of sliding speed and load existed between mixed and hydrodynamic lubrication regimes. This study suggests that the SLM-IP Cu NPs method is a promising approach for friction reduction surface microtexture manufacturing.