Friction characteristics of mechanically microtextured metal surface in dry sliding

Improving tribological properties by applying various textured surfaces have been reported by many researchers. In these studies, most utilized surfaces have been textured with lasers. However, such a texturing method contains several problems including thermal effects, formation of pileups, possible dimple shapes, and lower efficiency than mechanical methods. The traditional mechanical texturing methods also have some problems. In this study, an alternative method is developed by using vibration-assisted microcutting with a cube-corner diamond indenter which is vibrated in the depth direction with an amplitude of tens of microns or less. In this technique, the pileups generated around all the dimples in texturing can be removed by supplementally conducting a normal microcutting on the machine. By the developed method, textured surfaces of brass plate (c2680), in which micro dimples transferred tip shape of the indenter were regularly arranged at a period of tens of microns, were successfully manufactured. In order to verify their potentials, dry sliding tests using steel balls (534A99) were conducted on the surfaces textured by both the proposed and the normal cutting methods for comparison. Subsequently, the influence of the removing pileups and the dimple density were also examined through the dry sliding tests. A series of the sliding test results were analyzed through the monitored friction coefficients, wear rates, and observations of worn surfaces and generated debris. As a result, textured surface with a relatively high area density, such as 40% where pileups were completely removed showed the lowest friction coefficient and wear due to the trapping and reducing effects of the generated wear debris and real contact area by the periodically arranged micro dimples. Therefore, the proposed texturing method can be a new candidate to produce the surface textures for better tribological properties. Also, higher texturing efficiency could be realized by just applying higher sample rotation speed and/or vibration frequency.