Micro-texturing of DLC Thin Film Coatings and its Tribological Performance Under Dry Sliding Friction for Microforming Operation

Abstract

As an approach to enhance the tribological performance of diamond like carbon (DLC) coating films for dry microforming operations, the present study applied the micro-textured structures to the DLC films. Micro-texturing was realized by using stainless steel wire mesh as a masking during the ionized physical vapor deposition (I-PVD) of DLC films. Tribological performance of fabricated micro-textured structures with a width of 40 and 80μm and an interval of 30 and 40μm were evaluated by the ball-on-disk type friction tester. To simulate the severe contact state of dry microforming operation, normal pressure of 1.2GPa was applied for 100,000 times rotations under unlubricated condition. As results, the micro-textured DLC films with structure size of 40μm showed the excellent stable variation with relatively low coefficient of friction (COF) of μ = 0.01-0.06, while the conventional non-textured DLC films showed the significantly large deviation with high COF of μ > 0.25. In comparison between the different micro-texture sizes, the smaller structure size of 40μm showed the lower COF than that of 80μm, although the larger amount of wear debris from DLC films were generated. Additional wear track observation after the friction tests revealed that the stable tribological properties of textured DLC films were attributed to the promotion of wear debris ejection, which can prevent the plowing inside the apparent area of contact.