PVD-COATINGS FOR WEAR PROTECTION IN DRY CUTTING OPERATIONS

Many ecological and economic problems in manufacturing are caused by t he use of coolants. The benefits of coolants in cutting processes are reduced friction in the tool-workpiece contact (lubricating-effect) an d transport of thermal energy dissipated in the contact zone (cooling- effect). Coatings separate the tool from the workpiece material and of fer. when combined with cutting materials of high hot hardness, the po ssibility to replace coolants. Especially, the addition of aluminum to the TiN-coating system shows remarkable advantages for lubrication-fr ee cutting operations. The formation of amorphous aluminum oxide on th e top of the coating protects the film from further oxidation at high temperatures. In dry drilling of tempered steel the wear mechanisms of different coated WC-cemented carbide and cermet tools have been inves tigated. Due to the increased oxidation stability, especially of (Ti,A l)N-layers with a high content of aluminum, a superior wear behaviour in dry machining was found. (C) 1997 Elsevier Science S.A.