The development of sputtered carbon based coatings incorporating Cr, Ti, Band N

Sputtered carbon coatings have been reported to have excellent tribological properties (low friction coefficient and low wear rate) and, therefore, th e potential to be used as hard-solid-lubricant wear-resistant coatings. Fur ther development of the sputtered carbon-based coatings has been carried ou t and the inclusion of Cr, Ti, B and N to deposit composite or multilayer c oatings has been studied. The deposition process was designed to deposit a 2.0 mum CrTiBCN base layer followed by a 2.0 mum CCrTiB tribological top la yer using unbalanced magnetron sputtering with one chromium, one titanium d i-boride, and two carbon targets with a three axis substrate rotation mecha nism. The base layer was found to have a hardness of approximately 2500 HV, a critical scratch load of L-c > 80 N, and a friction coefficient of mu > 0.4 against a WC ball in air, similar to those of conventional hard coating s (TiN for example). The tribological top layer was shown to have both high hardness (similar to 2200 HV) and low coefficient of friction (similar to 0.06 under a load of 80 N in pin-on-disc tests). The nitrogen gas flow rate for deposition of the base layer, and the sputtering powers on the chromiu m and titanium di-boride targets for the deposition of the tribological top layer were optimized to produce coating's with the best combination of har dness, low friction and low wear rate; Pin-on-disc tests in air and recipro cating wear tests in air, in water and in oil were used to determine the tr ibological performance of the coating. The results indicated that this new composite coating could be used as a hard, solid lubricant film for a range of mechanical applications. (C) 2000 Elsevier Science B.V. All rights rese rved.