Friction and wear reduction effect of laser powder bed fusion produced Voronoi structures in lubricated metal-polymer sliding pairs

The failure of artificial joints is often attributed to wear, prompting researchers to explore effective solutions such as material improvement, surface texturing and coating. This study introduces a novel approach of employing 3D printed Voronoi structures to enhance lubrication in polymer-metal sliding wear, with the aim of extending the longevity of artificial joint systems. Specifically, this study investigates the relationship between the geometries and tribological properties of Ti6Al4V Voronoi structures, paired with ultra-high-molecular-weight polyethylene (UHMWPE). The results indicate that the void size in Voronoi structures can be manipulated to match the feature size in the surface texturing approach, suggesting the potential to induce the hydrodynamic effect for friction reduction. The effect of Voronoi structures on reducing friction and wear was examined using pin-on-disc (PoD) tests. In comparison to the control group of solid pins, implementing Voronoi structures in the pins decreases the mean values of static coefficient of friction (COF), dynamic COF, and wear volume by 24.6 %, 29.4 %, and 51.2 %, respectively. Indistinct trends were observed between the COF and the geometric parameters of Voronoi structures. It is hypothesised that interconnected porosity networks within Voronoi structures may preserve wear debris and retain lubricant, potentially elevating hydrodynamic pressure and thereby improving the friction condition. Moreover, comparative analysis of the wear tracks confirms the effective wear reduction achieved by Voronoi structures, with abrasion identified as the primary wear mechanism.