Relevance of friction and wear characteristics to surface topography of GCr15 steel processed by electropolishing

Abstract The surface topography directly affects the friction and wear properties of GCr15 steel, and different processing methods can obtain different surface topography. To investigate the relationship between surface topography and friction performance under various friction conditions, GCr15 steel surfaces were treated using electropolishing and lapping techniques, followed by a reciprocating sliding friction test on a UMT-3 friction tester. Surface topography parameters, including contour support length ratio ( R mr ), reduced valley depth ( R vk ), and core roughness ( R k ), were selected to evaluate the surface topography post-processing. The results indicate that, under dry friction conditions, electropolishing reduces surface micro-peaks through electrolytic ablation and passivation, which increases the surface profile support length ratio. This enhanced support length ratio improves load-bearing capacity and reduces wear, with an observed inverse relationship between support length and the friction coefficient. For samples with similar surface roughness, electropolished surfaces exhibit a friction coefficient of 0.401 ± 0.01, compared to 0.574 ± 0.02 for lapped surfaces—demonstrating a 30% reduction in friction for the electropolished surfaces. Under oil lubrication conditions, electropolishing increases the K value ( R vk / R k ) of the sample surface, which improves oil retention, reduces the friction coefficient, and enhances anti-friction performance. For samples with similar surface roughness, the friction coefficients are 0.151 ± 0.01 for the electropolished surface and 0.163 ± 0.01 for the lapped surface—indicating a 7% reduction in friction for the electropolished sample. These findings suggest that electropolishing treatment of GCr15 steel surfaces effectively reduces wear and enhances wear resistance during frictional processes.