Effect of laser textured surface on the friction coefficient of wheel/rail under dry friction condition

In this study, laser surface texturing was adopted to create discretely distributed microtextures on wheel specimens, with the aim of enhancing surface roughness and, consequently, increasing the friction coefficient. Through an orthogonal experimental methodology, the effects of laser processing parameters—specifically, single-pulse laser energy, the distance between adjacent laser-textured pits, and laser defocus distance—on surface roughness were investigated. This study identified the most significant influencing factors and selected optimized processing parameters to control the morphology of laser texturing. Two typical laser texturing morphologies, namely, volcanic crater type and spherical crown type, were reconstructed through modeling. A comprehensive analysis was conducted on the variation in surface roughness under different texture dimensions, distribution intervals, and arrangement configurations. Finally, rolling friction coefficient tests were conducted using a friction-wear testing machine. The results show that laser texturing significantly enhances the friction coefficient between the wheel and rail. For nontextured specimens subjected to approximately 1000 MPa of contact pressure, the friction coefficient stabilizes at around 0.24 with a slip ratio of approximately 0.45%. In contrast, the laser-treated specimens exhibit an improvement in the friction coefficient ranging from 51.3% to 62.5% compared to their untreated counterparts. Furthermore, lower single-pulse laser energy processing increases the friction coefficient between the wheel and rail; however, the resulting laser-textured morphology exhibits inferior wear resistance compared to those produced with relatively higher pulse energies.