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Roughness analysis of electrochemically textured surfaces: effects on friction and wear of lubricated contacts

Maskless electrochemical texturing (MECT) is an inexpensive and fast technique with great potential to produce surface textures on metallic surfaces at industrial scale. This work used MECT to produce arrays of chevrons onto AISI 1045 steel surfaces. Block-on-ring tests using standard rings and textured blocks investigated the effects of full and partial texturing on friction and wear. Two normal loads (216.9N and 315.0N) were applied to investigate the effects of the textures under mixed and boundary lubrication regimes. Under the lower load, MECT increased friction and wear rates. This was attributed to the surface roughening of the areas outside the chevrons, which reduced the ratio between the average roughness of the asperities and the hydrodynamic film thickness (λ ratios), shifting the lubricant regime from mixed to boundary lubrication. Partial texturing performed better than full texturing, but no clear trend was found for the position of the textured potion either at the inlet or the outlet of the contact. On the other hand, for the higher normal load, both smooth and textured samples operated under boundary lubrication, so that the effect of the pockets to supply additional lubricant to the contact resulted in reduced friction and wear. Entrapment of wear debris within the chevrons was found for both normal loads, which avoids the presence of hard debris in the contact, thus also contributing to reduce friction and wear. The Kruskal-Wallis test was applied, and it was observed that the factors, load and surface, produced statistically significant effects on friction coefficient values.