Magnetron sputtering of Cr(AI)N coatings:: Mechanical and tribological study

CrN coatings produced by magnetron sputtering are routinely deposited on tools and components for machining and forming applications. This paper reports on the effect of additions of aluminium (< 15 at.%) on the mechanical and tribological properties of CrN coatings. Alummium has been incorporated into CrN by co-sputtering of chromium and aluminium in a mixture of argon and nitrogen. Mechanical properties have been evaluated by ultramicroindentation techniques and scratch testing, while tribological tests have been carried out against ball bearing steel and titanium alloy balls by the pin-on-disc method. The thermal stability and oxidation resistance of the coatings have also been examined. A significant increase in hardness, reaching values up to 35 GPa, has been achieved for the CrAIN coatings when compared to CrN coatings. The improvement in tribological properties has also been remarkable, with a decrease in friction coefficient against bearing steel and also a non-adhesive wear mechanism against titanium alloy balls. In addition, the CrAIN coatings exhibited higher thermal stability than pure CrN coatings. (c) 2005 Elsevier B.V. All rights reserved.