Performance of oxygen-rich TiALON coatings in dry cutting applications

Special research activities are concentrated on optimizing coating properties for improving the performance of tools in dry cutting applications. TiAlN-based hard coatings for dry cutting operations are well known for their high microhardness even at elevated temperatures as well as for their good oxidation resistance. A further improvement can be achieved by adding oxygen to deposit TiAlON. In dry drilling of tempered steel the wear mechanisms of oxygen-rich TiAlON-coated WC-carbide tools were investigated. Two possible approaches for plating TiAlON were examined: high ion sputtering (H.I.S(TM)) and the conventional magnetron sputter ion plating (MSIP). Graded and multilayer TiAlON coatings with varying oxygen contents were developed. Effects of the used deposition technology on coating structure, coating composition, strength and microhardness, as well as their influences on cutting performance were investigated. Highlighted are influences of oxygen-rich layers on wear behavior of TiAlN coatings in dry machining. Coating properties were characterized by SEM and EDX. Film adhesion was analyzed by scratch tests. In spite of reduced microhardness of TiAlON coatings high abrasive wear resistance in dry drilling of tempered steel could be reached due to improved high-temperature properties of TiAlON films. (C) 1998 Elsevier Science S.A. All rights reserved.