New hard/lubricant coating for dry machining

Environmental and economic considerations have emphasized the trend for more dry machining. Advanced wear-resistant coatings with increased oxidation resistance such as PVD TiAlN offer an advantage for dry machining of cast iron and alloyed steel. Although some important cutting operations are still not possible without coolants, further possibilities for dry drilling and tapping of steels are enabled by the recent approach using tools with hard coating layers topped with a lubricant layer. The combination of hard/soft coating layers allows improved chip flow with a lowered coefficient of friction and reduced cutting force. In this work, the hard/soft coating consists of a low-internal-stress TiAlN (hard layer) and WC/C (lubricant layer) of medium microhardness and low coefficient of friction. Both coating types are produced economically and reproducibly in one production scale PVD coating system. Recent performance data from field tests will be presented. (C) 1999 Published by Elsevier Science S.A. All rights reserved.