Laser-induced particle impact testing for improvement of tribological performance: Micro-dimpled textures with solid lubricant bonding

Molybdenum disulfide (MoS2) is widely used as a solid lubricant, owing to its layered crystalline structure. However, for tribological performance, the stable bonding of solid lubricants to metallic substrates remains a critical issue. In conventional methods, solid lubricants dispersed in grease are sprayed and deposited onto the substrate surface. However, the lubricant layer may delaminate and disappear during frictional contact. Here, we employ laser-induced particle impact testing (LIPIT), which ejects micro-sized particles at high velocities via laser ablation. Particle impact with high velocity induces severe plastic deformation, forming deep micro-dimples that can retain lubricants and improve tribological performance. We propose a two-step LIPIT: the first step deposits and bonds MoS2 particles and the second step generates micro-dimple structures through the impact of hard particles. The treated surface is characterized using energy-dispersive X-ray spectroscopy, focused ion-beam analysis, and transmission electron microscopy, revealing that the MoS2 is strongly bonded at the crater center (lowest depth). Frictional tests with ball-on-disk contact sliding indicate that micro-dimples with adhered MoS2 created by LIPIT function as lubricant reservoirs and significantly improve tribological performance. The results show that our proposed LIPIT-treated surfaces exhibit both a reduced friction coefficient and enhanced resistance to seizure.