Tribological and mechanical properties of CNx- and SiCNx-TiN/Ti multilayered systems grown onto steel

One of the major problems of CNx-based hard coatings for mechanical applications is their poor adhesion to steel substrates. In the present case, a TiN/Ti gradient underlayer has been deposited between the carbon nitride films and a high-speed steel substrate by means of magnetron sputtering. The same method was used to grow different CN, top layers in which various deposition parameters (Ar/N, ratio, DC bias) were varied. A silicon-doped CNx film was also prepared by dosing a certain amount of the gaseous precursor Si(CH3)(3)Cl in the reaction chamber. Scratch tests have shown that the introduction of the underlayer leads to an improvement of the adhesion in all cases. Tribological measurements clearly indicate that a good adhesion between the substrate and the coating is always needed in order to obtain low and stable friction coefficients. The wear rate and nanohardness of the samples have been also studied in relation with the different growing conditions. The results show an improvement of the adhesion, hardness and wear resistance without an increase of the friction coefficient for the samples synthesised using Ar/N, mixtures and DG biasing of the substrate during deposition. (C) 2002 Elsevier Science Ltd. All rights reserved.