SPUTTER DEPOSITION OF ULTRAHARD COATINGS WITHIN THE SYSTEM TI-B-C-N

Ultrahard (hardness greater than 4000 HV 0.05) coatings derived from TiB2 were investigated as thin, wear-protective coatings for cutting tools. Deposition methods were based on non-reactive as well as reactive sputter deposition employing d.c. magnetron sputtering from TiB2 targets. Coatings were deposited onto molybdenum, niobium and cemented carbide substrates. Very fine-columned films with an (001)-oriented TiB2 phase are formed by means of non-reactive sputtering of TiB2 targets. Coatings deposited reactively in Ar-N2-C3H8 atmospheres exhibit very fine-grained to fracture-amorphous structures. In the case of reactive sputtering in Ar-N2 gas mixtures a hexagonal TiB2-xNy phase appears at low N2 flows. An increase of the N2 flow results in the formation of an additional phase based on TiN. Reactive deposition in Ar-C3H8 atmospheres leads to the existence of mixed-phase structures with phases based on TiB2 and TiC. Quarternary films grown in Ar-N2-C3H8 mixtures show multiphase structures consisting of phases based on TiB2 as well as TiC and TiN. Vickers microhardness measurements on coatings 3 - 5 μm thick on cemented carbide inserts gave the following maximum HV 0.05 values: Ti-B films 4000; Ti-B-N 4800; Ti-B-C 4000; Ti-B-C-N 4200. Stresses were found to be compressive with values up to 4 GPa. The results of scratch tests indicate very good adherence. Ti-B-coated cemented carbide inserts have been tested in the turning of aluminum alloys with promising results. © 1990.