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 temperatu re 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 composi tion, and microhardness was studied. It was shown that a solid solutio n (Ti,Zr)N was formed in the Ti-Zr-N coatings, in which the elements T i, Zr, and N were distributed homogeneously. The films had a fine stru cture. 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, i ncreasing 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 co atings. The (Ti,Nb)N grains were randomly oriented. A maximum microhar dness of 51.5 GPa was obtained for the Ti-Nb-N film deposited at a nit rogen pressure of 1.33 Pa. Increasing the nitrogen pressure to 2 Pa de creased the microhardness to 31.5 GPa. (C) 1998 Elsevier Science S.A. All rights reserved.