Surface and Coatings Technology 163 –164 (2003) 238–244 0257-8972/03/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0257-8972 Ž 02 . 00477-2 Wear protective coatings consisting of TiC–SiC–a-C:H deposited by magnetron sputtering T. Zehnder , J. Matthey , P. Schwaller , A. Klein , P.-A. Steinmann , J. Patscheider * a b a b b a, a EMPA, Uberlandstrasse 129, CH-8600 Dubendorf, Switzerland ¨ b EICN, 7, Avenue de l’Hotel-de-Ville, CH-2400 Le Locle, Switzerland ˆ Abstract Hard coatings of the composition Ti Si C which consist of TiC, TiSi , a-SiC and a-C:H, have been deposited with the aim of x y z x depositing self-lubricating Ti SiC . The films were prepared by reactive unbalanced magnetron sputtering from elemental titanium 3 2 and silicon targets in the presence of argon and acetylene. The coatings are composed of nanocrystalline TiC and, depending on the composition, of titanium silicides, amorphous hydrogenated carbon and amorphous silicon carbide. Nanohardness values of up to 30 GPa could be obtained for coatings with friction values below 0.25 against steel in an unlubricated pin-on-disk setup. Low friction coefficients against steel were measured for higher concentrations of amorphous carbon at hardness values of approximately 15 GPa. In contrast to coatings composed of titanium, silicon and nitrogen, the hardness maximum is observed at TiC grains sizes of 25 nanometers.  2002 Elsevier Science B.V. All rights reserved. Keywords: Magnetron sputtering; Nanocomposites; Hard coatings; XPS; X-ray diffraction 1. Introduction Wear-protective hard coatings of single-phased mate- rials are widely used in industry since 30 years to increase the lifetime of tools and wear-exposed compo- nents. High hardness is one of the important properties when coatings have to protect a component from exces- sive wear; however, coatings with high hardness alone are unlike to satisfy the complex needs of practical applications of tools and machinery components. Low friction, especially by dry lubrication, and low wear rates as a consequence of tribochemical processes, are characteristics of coatings that are of prime importance in a variety of applications such as roller bearings, sliding bearings, extruders, etc. Coatings with outstand- ing thermal stability are required when wear processes with temperatures exceeding 800 8C challenge the sta- bility of protective coatings, as in the case of drill bits, high speed dry machining and many more. Nanocom- *Corresponding author. Tel.: q41-1-823-43-65; fax: q41-1-823- 40-34. E-mail address: joerg.patscheider@empa.ch (J. Patscheider). posite coatings containing amorphous phases with good high-temperature stability are such materials that meet these requirements. The best studied example for the latter case are nc-TiNya-SiN coatings prepared by x different groups w1–6x. Nanocomposite coatings with amorphous hard carbon (a-C:H) show low friction and high hardness as is observed for nc-TiCya-C:H w7x and for nc-TiCya-C w8,9x. The low friction is due to the presence of the amorphous hydrogenated carbon phase, which trans- forms into graphitic phases and thus acts as a solid lubricant. In analogy to the previously obtained results on nc- TiCya-C:H w7x, attempts have been undertaken to depos- it thin nanocomposite films with increased hardness and low friction behavior. In the present paper we report on the preparation and characterization of coatings contain- ing titanium, silicon, carbon and hydrogen; similarities and differences to the aforementioned coating materials are discussed. The Ti–Si–C phase diagram was experimentally determined by Bruckl w10x at 1473 K for sintered powders. He found two ternary phases, one named T1