Structure, mechanical and tribological properties of nitrogen-containing chromium coatings prepared by reactive magnetron sputtering

Cr1-xNx coatings were deposited by magnetron sputtering at a substrate temp erature of 200 degrees C onto AISI 316 stainless-steel substrates immersed in an Ar/N-2 plasma. The goal of this investigation was to study the influe nce of nitrogen content on the structural, mechanical and tribological prop erties of the Cr1-xNx coatings (with x being in the range of 0-0.4). The co ating composition and microstructure were evaluated utilizing glow discharg e optical emission spectroscopy and glancing angle X-ray diffraction. where as the morphology was evaluated by scanning electron microscopy. Knoop micr ohardness, scratch adhesion, pin-on-disc sliding, ball-on-plate impact and abrasive wheel wear tests were performed to evaluate the mechanical and tri bological properties. The presence of Cr, Cr2N, CrN (and mixtures of these phases) has been identified and related to the film composition. For Cr1-xN x coatings with x less than or equal to 0.16, only the alpha-Cr phase could be detected. A progression towards a denser microstructure was found with increasing nitrogen content up to x = 0.29, associated with an increase in hardness from 700 up to 2400 HK0.025. Cr1-xNx coatings with x = 0.10-0.16 s howed good adhesion and the best abrasive and pin-on-disk sliding wear resi stance, together with less crack development around the indentation area (a nd thus improved toughness) in impact tests after 50 000 impacts, against b oth steel and cemented tungsten carbide balls. The hardest coating (Cr0.71N 0.29) performed best in terms of reducing the resulting impact indentation volume. (C) 1999 Elsevier Science S.A. All rights reserved.