Preparation, characterization and wear behaviour of TiN(x)-coated cermets obtained by plasma-enhanced chemical vapour deposition

Commercial cermet inserts were coated with titanium nitride by plasma-enhanced chemical vapour deposition (PECVD) using a pulsed direct current (d.c) glow discharge. The influence of the coating parameters on the deposition rate, on the layer composition, on the layer- substrate interface, on the structure and on the microhardness of the layers was investigated for deposition temperatures in the range 500-700 Grad C. The adhesive strength, and some mechanical properties, of the coated cermets were characterized by scratch tests, by friction wear investigations and by measurments of the transverse rupture strength. The wear behaviour was examined in the cutting tests. It was found that TiNx-coatings deposited with a sufficiently high deposition rate and plasma power density have a low oxygen and chlorine content and that they are nearly stoichiometric. The layers usually have a columnar structure with a (200) texture. A granular, equiaxed structure was observed within a small range of deposition conditions. In interrupted and continuous turning tests with steel and grey cast iron, a high cutting performance of the coated insertes, which depended on the coating thickness and on the deposition temperature, was achieved.