Ultrahard Ti-B-N coatings obtained by reactive magnetron sputtering of a Ti-B target

The influence of the chemical composition of TiBN compounds on their properties was studied using cathodic reactive magnetron co-sputtering from a Ti and a TiB2 target. Five experiments have allowed to obtain 70 different composition points with N and B contents comprised between 0 and 60 at.%. Two domains with hardness over 50 GPa were identified. Only one domain shows very high abrasive wear resistance in water. The composition of this area is centred on compounds containing 20% B, 27% N and 53% Ti. A Ti-B target was then sintered to obtain this composition from a single target. By varying the nitrogen flow, one material with high abrasive wear resistance was elaborated. This material shows a f.c.c. structure with a lattice parameter of 0.432 nm. This coating contains 19% B, 26% N and 55% Ti. The microhardness was measured to be 44 GPa. Scratch testing indicates a cohesive failure mode with a critical load of 30 N. The abrasive wear resistance appears to be at least three times better than the wear resistance of TiN or CrN. The results obtained by co-sputtering and by sputtering of the Ti-B target show good correlation. (C) 1998 Elsevier Science S.A. All rights reserved.