Deposition of diamond-like carbon films containing metal elements on biomedical Ti alloys Da-Yung Wang a , Yin-Yu Chang a, * , Chi-Lung Chang a , Yu-Wei Huang b a Institute of Materials and Systems Engineering, Mingdao University, Taiwan b Department of Materials Engineering, National Chung-Hsing University, Taiwan Received 26 April 2004; accepted in revised form 14 April 2005 Available online 13 June 2005 Abstract Three kinds of diamond-like carbon (DLC) films, which contain different metals (Ti, Cr, Zr) and different interface designs, were deposited on biomedical titanium alloy (Ti– 6Al– 4V, ASTM F136) by using a cathodic arc evaporation system. Preliminary results showed that the DLC films are hydrogenated, amorphous and dense in structure. Scratch tests and Rockwell indentation tests reveal that the graded structures can improve the adhesion of DLC films. The Raman analyses showed that the Cr-containing DLC films possess lower I D /I G ratio, lower G-peak positions, and higher coating hardness. The pin-on-disk wear test in different environments (air and simulated body fluid) revealed that all the DLC films improve the wear performance of the substrates, and the wear coefficient is lower in simulated body fluid than that in air. In addition, the Cr-containing DLC films exhibited the lowest friction coefficient of 0.06 in simulated body fluid and 0.16 in air with the counterface of UHMWPE. Because of their dense structure, good adhesion and superior corrosion resistance in SBF, the Cr-C:H/ CrN films exhibited significantly low friction in SBF. The ICP-MS analysis revealed the release of Cr ion is 2.22– 10.03 ppm from the Cr- contained DLC films, which is less than that from Co – Cr – Mo alloy (106.17 ppm), showing that the Cr-containing DLC films meet the requirement of biomedical applications. The potentiodynamic test revealed that the corrosion resistance of the ASTM F136 titanium alloys is increased substantially by the metal-containing DLC coating. D 2005 Elsevier B.V. All rights reserved. Keywords: Cathodic arc; Diamond-like carbon; Titanium alloy 1. Introduction Titanium alloys are widely used in biomedical applica- tions due to their good mechanical properties, corrosion resistance and low density. However, the poor tribological properties are their disadvantages. Over a long period of using time, the artificial thighbone rubbing against hipbone would produce wear debris which cause inflammation and osteoclast cell increased when large wear debris contacted human cell. Those effects lead to the losses and failure of artificial hip joint [1,2]. Surface modification by hardening of the titanium alloy is a key process to strengthen biomaterials in clinical applications [3–6]. Diamond-like carbon (DLC) films are suitable for the surface modification of titanium alloys, and they have many desirable properties such as high hardness, low friction coefficient, chemical inertness, and non-toxicity, etc. Vari- ous in-vitro and in-vivo studies on biological effects of DLC coatings have been performed and the usability of DLC films as biomaterials has been verified [7–10]. The major disadvantage of DLC films is low adhesion resulting from high internal stress. Some efforts have been directed toward improving the adhesion of DLC films by depositing an interlayer or graded interlayers between the DLC film and the substrate [11–13]. Intermediate layers of Ti, Zr, W, Nb, Si, Cr or WC have demonstrated their potential in improving film adhesion and wear properties [14–21]. Among various PVD processes, cathodic arc activated deposition process synthesizes DLC films with doping materials simultaneously [22–24]. Transition metals, in- 0257-8972/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2005.04.017 * Corresponding author. E-mail address: yinyu@mail2000.com.tw (Y.-Y. Chang). Surface & Coatings Technology 200 (2005) 2175 – 2180 www.elsevier.com/locate/surfcoat