Tool Wear in Titanium Machining

Abstract

Summary The mechanism controlling the crater wear of cutting tool materials in the machining of titanium alloys has been shown to be fundamentally different than that in the machining of steel and nickel-based alloys. It is suggested that tool wear is greatly reduced when adhesion occurs between the tool and the chip, preventing relative sliding at the tool/chip interface. This adhesion is promoted by chemical reaction at the interface. The thickness of the reaction layer is determined by the balance between the diffusion flux of tool constituents through the layer and the removal of tool constituents through chemical dissolution at the interface between the reaction layer and the titanium chip. In this way, for given cutting conditions, a characteristic thickness of the reaction layer is maintained and tool wear is limited by the rate of dissolution of the reaction layer into the titanium. The existence of a stable reaction layer of Tic on diamond and WC-based tools (the two most wear-resistant tool materials) has been demonstrated, and the estimated diffusion flux correlates well with the observed wear rate.