Turning of titanium alloy with TiB2-coated carbides under cryogenic cooling

TiB2 is a relatively new coating material used on carbide cutting tool inserts and is useful owing to its high hardness and chemical inertness. In the present investigation, TiB2-coated carbide inserts were used to machine titanium alloy (Ti-5Al-5Mo-2Sn-V) under dry as well as cryogenic cooling conditions. The cutting forces, surface quality, surface roughness and tool wear were studied in detail. Although beneficial effects of machining under cryogenic cooling, reported in previous investigations, were observed in the present investigation, TiB2 as a coating material on carbide inserts was found to be unsuitable for machining titanium alloys. Removal of coating followed by severe abrasion, adhesion and diffusion was found to be the main reason for tool failure.