MICROMACHINING OF BRITTLE MATERIALS WITH SOLID COATINGS

Abstract

A strong dependence of coating thickness was observed to promote the delayed onset of crack formation on machined surfaces and minimize subsurface damage. This was attributed to a beneficial stress acting back through the shear plane and into the work material during cutting to increase the ductile mode cutting energy as demonstrated in an analytical model that captured theoretical slip activity of a single crystal. The reaction stress also decreased the resultant tensile stresses acting on cleavage planes, which were identified as the source for brittle mode cutting. The physical presence of the coating is considerable in micro-cutting with the demonstrated potential implementation to improve machinability of brittle materials.