Combining laser-textured dimples and AlCrN coating to reduce wear on AISI M2 steel

This work investigates the synergistic effect of femtosecond laser surface texturing (LST) and AlCrN coating on the wear performance of fine blanking tools. Dimple textures with 10, 15% and 20% surface coverage were fabricated on AISI M2 steel and coated with 1.5 µm AlCrN coating via HIPIMS. SEM and optical confocal microscopy confirmed the high geometrical accuracy of LST features and good coating adhesion at the coating-dimple interface. Contact angle measurements indicated that the as-coated surfaces were oleophilic, while increasing the textured area density led to a progressive shift toward higher contact angles, indicating a modification of lubricant spreading behaviour. Ball-on-disk tests were performed under loads of 10, 30 and 50 N trying to simulate fine blanking contact conditions. An initial lubricant supply of 0.05 mL was sufficient to maintain a stable separation film, resulting in friction coefficients between 0.10 and 0.14 regardless of textured area density. In terms of wear, uncoated dimple-textured surfaces did not yield beneficial behaviour, showing higher wear rates than the untextured surface. In contrast, the application of the AlCrN coating on the untextured surface resulted in an approximately 90% reduction in the wear coefficient. A comparable wear reduction was observed for the sample textured at 10% dimple density; however, further increases in texture density led to an exponential increase in wear rate. SEM/EDX observations indicate that debris entrapment within the dimples promote third-body abrasion, contributing to the increased wear at higher texture densities.