Multicomponent Ti-Zr-N and Ti-Nb-N coatings deposited by vacuum arc

A triple-cathode vacuum are plasma gun was used to deposit Ti-Zr-N and Ti-Nb-N multicomponent coatings onto cemented carbide (90% WC, 8% Co, 1.8% TaC, and 0.2% NbC) substrates. The coatings were deposited at a bias voltage of -40 V relative to the anode, and a substrate temperature of 400 degrees C. The influence of the nitrogen background pressure, which was in the range of 0.67-2 Pa, on the structure, phase composition, and microhardness was studied. It was shown that a solid solution (Ti,Zr)N was formed in the Ti-Zr-N coatings, in which the elements Ti, Zr, and N were distributed homogeneously. The films had a fine structure. The (Ti,Zr)N grains had an average diameter of 30 nm and were {111} orientated. The nitrogen concentration in the solid solution was not affected by the nitrogen pressure in the range studied. However, increasing the nitrogen pressure to 2 Pa increased the Zr concentration, while that of Ti decreased and a less dense structure is formed. The formation of a (Ti,Nb)N solid solution was observed in the Ti-Nb-N coatings. The (Ti,Nb)N grains were randomly oriented. A maximum microhardness of 51.5 GPa was obtained for the Ti-Nb-N film deposited at a nitrogen pressure of 1.33 Pa. Increasing the nitrogen pressure to 2 Pa decreased the microhardness to 31.5 GPa. (C) 1998 Elsevier Science S.A. All rights reserved.