Current understanding of surface effects in microcutting

Machining processes have made technological leaps in achieving ultraprecision material removal and surface finishing at the submicrometric scale. At this level of precision, size effects have dominated machining investigations while surface effects have often been overlooked. The majority of micromachining research works are ignorant of the potential implications that these phenomena bring as the characteristic length approaches the ultraprecision machining level. In this review, physicochemical and physical surface effects are discussed by examining the theoretical developments and applications of each phenomenon in machining. These effects include the Rehbinder effect, solid coatings, and extrusion-cutting. Substantial mesoscopic analyses have been performed on metals with the Rehbinder effect and extrusion-cutting but the inherently different material deformation characteristics in microcutting invite further investigations. While solid coating effects have been reported at the microscale, its discovery questions the influence of other inevitably formed surface coatings (i.e. oxide layers). To these ends, key areas for future research in the microcutting of engineering metals and brittle materials are proposed in addition to the integration with unavoidable size effects. As machining technology and material characterization techniques progress into the nanometric scale, there is a need to rally efforts towards the embrace of surface phenomena in microcutting.