Wear behaviour of fiber laser textured TiN coatings in heavy loaded sliding regime

In heavy loaded mating components, such as sliders and sliding bearings, it is very complicated to guarantee the efficiency of lubricant films for long times during severe service conditions. In this work, the benefits deriving from the use of fiber laser sources for surface texturing of very thin TiN coatings in severe wear working conditions were demonstrated. Evaluations of the laser textured dimples shape, geometry and density are given. Wear performance of the fiber laser textured surfaces was evaluated in discontinuous oil lubricated conditions with a flat contact. High normal load and low sliding speed were applied. Comparison tests were performed also on commercial TiN and WC/C coatings. In terms of average wear volume and of maximum wear depth Laser Surface Texturing of TiN provided respectively a 70% and a 45% reduction if compared to plain TiN. If compared to WC/C the wear resistance gains were lower but LST TiN maintained such benefits for longer wear runs. SEM analysis revealed also that the laser interaction provided a localized thermal cracking to the TiN coating. However, the sliding action caused very limited and localized coating fragmentation or delamination.