Ion implantation of superhard ceramic cutting tools

Despite numerous reports of tool life increase by ion implantation in machining operations, ion implantation applications of cutting tools remain limited, especially for ceramic tools. Mechanisms of tool-life improvement by implantation are not clearly established due to complexity of both implantation and tool-wear processes. In an attempt to improve performance of cubic boron nitride (CBN) tools for hard machining by ion implantation, a literature survey of ion-implanted cutting tools was carried out with a focus on mechanisms of tool-wear reduction by ion implantation. Implantation and machining experiments were then conducted to investigate implantation effects on CBN tools in hard machining. A batch of CBN tools was implanted with nitrogen ions at 150 keV and 2.5 x 10(17) ions/cm(2) and further used to cut 61 HRc AISI 52100 steel at different conditions. Results show that ion implantation has strong effects on part-surface finish, moderate effect on cutting forces, but an insignificant impact on tool wear. Friction coefficients, estimated from measured cutting forces, are possibly reduced by ion implantation, which may improve surface finish. However, surprisingly, 2-D orthogonal cutting to evaluate tribological loading in hard machining showed no difference on contact stresses and friction coefficients between implanted and nonimplanted CBN tools.