Mechanical and tribological properties of Cr–N and Cr–SI–N coatings reactively sputter deposited D. Mercs a, * , N. Bonasso a , S. Naamane a , Jean-Michel Bordes b , C. Coddet a a LERMPS, Universite ´ de Technologie de Belfort-Montbe ´liard (UTBM), Site de Montbe ´liard, F-90010 Belfort Cedex, France b PSA Peugeot Citroe ¨n, Technical center of Belchamp, F-25420 Voujeaucourt, France Available online 17 May 2005 Abstract Cr – N and Cr – Si – N coatings have been deposited with two nitrogen flow rates, 6 and 10 sccm, for a constant argon flow rate of 20 sccm with various amounts of silicon, in an ALCATEL SCM 650 sputtering system. DC and pulsed DC were used to power the target and the silicon coupons, placed in the erosion track, whereas the substrate holder was RF biased. All the deposited coatings are dense and well bonded to the M2 steel substrates. At 10 sccm N 2 , the increase of the silicon content up to 2.5 at.% into the coating leads to a maximum hardness (H) and a low Young’s modulus (E). A further increase of the Si content yields to both the decrease of H and E. At 6 sccm N 2 ,a similar but less pronounced phenomena are observed. Ball on disk tests under a normal load of 5 N applied to a 100Cr6 ball were performed to investigate the wear resistance of the coatings. Cr – Si – N coatings showed low friction coefficients and no measurable wear after 500 m of sliding at 0.2 m s À1 . D 2005 Elsevier B.V. All rights reserved. Keywords: Magnetron sputtering; CrN; Silicon; Nanocomposite; Wear 1. Introduction CrN is a well-known hard and very stable nitride coating, usually employed for severe wear and corrosion resistance applications, while Cr – N-based coatings con- taining a small amount of silicon have recently shown promising nanocomposite properties [1–4] such as enhanced hardness as well as high temperature oxidation resistance. Thus, new Cr–N-based coatings appear to be of prime interest for the substitution of electrolytic hard chromium coatings. In this study, the condition of formation, the mechanical and the tribological proper- ties of Cr–N-based coatings containing silicon are investigated. 2. Experimental CrN and CrSiN have been deposited in an Alcatel SCM 650 chamber equipped with a horizontal balanced magnetron cathode, powered with an Advanced Energy Pinnacle Plus pulsed DC generator, and an RF powered (13.56 MHz) substrate holder, set in order to keep the substrate surfaces at 90 mm from the target. The silicon content of the coatings was controlled by means of insulating polycrystalline silicon coupons (1 cm 2 ) placed in the erosion track (around 177 cm 2 ) of the chromium target (99.99% and 200 mm in diameter), with a varying total area of 0 to 10 cm 2 . Prior to deposition, all the M2 steel substrates were manually polished, ultrasonically cleaned in an acetone/ alcohol mixture for 10 min and placed in the chamber until a minimum pressure of 5 Â 10 À3 Pa was reached. Then, the chamber was backfilled with a constant argon flow rate of 20 sccm to regulate an argon pressure of 0.2 Pa. After an RF ion cleaning stage of the substrates (400 W/15 min), a thin adhesive layer of Cr or Cr–Si 0257-8972/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2005.02.214 * Corresponding author. Tel.: +33 3 84 58 37 01/+33 6 25 40 52 33; fax: +33 3 84 58 37 37. E-mail address: david.mercs@utbm.fr (D. Mercs). Surface & Coatings Technology 200 (2005) 403 – 407 www.elsevier.com/locate/surfcoat