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ur types of W-doped graphite-like carbon (W-GLC) films were deposited under different W target currents by magnetron sputtering method. The effects of W content on the microstructure and properties of the W-GLC films were analyzed via various characterization techniques. The results show that the microstructure of the W-GLC films tends to be loose, while the surface roughness distinctly increases with the increase in the W target current. Moderate W-doping can considerably improve the mechanical properties and wear resistance of the film, which will subsequently decrease as the W content becomes excessive. Moreover, the friction coefficient of the W-GLC films does not show a distinct change, but significantly increases when the W target current increases from 0.9 A to 1.2 A. In particular, when the W target current is 0.6 A, the friction coefficient and the wear rate of the W-GLC film are 0.02 and 3.8  10 17 m3/N
m, respectively, exhibiting excellent tribological properties.

I. INTRODUCTION

Graphite-like carbon (GLC) films, developed from diamond-like carbon (DLC) films, are a type of amorphous carbon film mainly composed of sp2 hybrid bonds. It not only presents the same excellent tribological properties as that of DLC films, but also shows good mechanical properties and load-bearing capacity.1–4 Currently, GLC films have primary application in tools and molds owing to their excellent performance. Compared to the conventional ceramic-coated tools, a cutter coated with a GLC film has a significantly longer life cycle. In addition, GLC films show great potential for surface protection and lifetime extension of the mechanical components working in water or oil lubricating environments and key friction components in the medical industry.5–8 Hence, GLC films provide a new approach to solve several problems facing DLC films, such as the high internal stress, relatively poor environment adaptability, and high-temperature stability, and opens up the possibility of implementing amorphous carbon films in more rigorous conditions.9 However, present literature mainly concentrates on the study of pure GLC films, and less attention has been paid to the influence of element doping on the microstructure and performance of GLC films. W, a type of typically strong carbide-forming metal, easily combines with carbon to form WC or W2C crystals, which possess low diffusivity and high thermostability.10 Contributing Editor: Mauricio Terrones a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.433

Numerous studies have shown that11–16 in a certain range of content, W-doping is an effective way to improve the mechanical strength, toughness, thermostability, and oxidative stability of DLC films. Hence, currently, W-doped DLC films are an important topic in the study of metal-doped DLC films. However, to the best of our knowledge, research on W-doped GLC films, especially on the relationship between the quantity of W-doping and the microstructure and performance of films, has not been systemically reported. In this study