In this study, cutting performance of CBN tools and PVD-coated carbide tools in end-milling of hardened
steel was investigated. In high-speed dry hardmilling, two types of CBN tools were applied: the CBN-rich
type and an ordinary one. In the case of relatively low-speed milling, on the other hand, a few coated
carbide tools were selected where four kinds of coating films, TiN, TiCN, TiAlN and multi-layered TiAlN/
AlCrN, were deposited on the K10 and P30 grade carbide. The cutting performance was mainly evaluated
by tool wear, cutting temperature, cutting force and surface roughness. In dry cutting of hardened carbon
steel with the ordinary CBN tool, the cutting tool temperature rose rapidly with increase in cutting speed;
and tool temperature reached approximately 850 1C at the cutting speed of 600 m/min. In the case of the
CBN-rich tool, the cutting temperature decreased by 50 1C or more because of its high thermal
conductivity. It is remarkable that tool wear or damage on a cutting tool was not observed even when
the cutting length was 156 m in both CBN tools. In the case of coated carbide tools, the temperatures of
TiN-, TiCN- and TiAlN-coated carbide tools rose as cutting proceeded because of the progress of tool wear,
but that of TiAlN/AlCrN-coated carbide tool hardly rose due to little tool wear.When the base material was
K10 grade carbide, tool temperature was lower than that of P30 with any coating. The tool flank wear
depends considerably on hardness and oxidizing temperature of the coating film.