Effect of change in temperature on the tribological performance of micro surface textured DLC coating
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In this study, surface texturing and hydrogenated amorphous carbon (a-C:H) diamond-like carbon (DLC) coating was combined to evaluate the coating performance at various temperatures in oil lubricated reciprocating sliding tests. Micro dimples were created by laser surface texturing on M2 steel using a Pico second laser. DLC coating was deposited by hybrid magnetron sputtering on textured substrates. Textured a-C:H showed stable coefficient of friction at 30, 80, and 125 °C compared to un-textured a-C:H. At 30 °C, graphitization was not observed for both textured and un-textured DLC coating. Graphitization was more pronounced in the case of un-textured a-C:H at 80 and 125 °C. Results show that, at all temperatures tested (30–125 °C), DLC textured samples showed higher wear resistance compared to un-textured DLC coating. The improvement in wear resistance can be explained by the lower graphitization of textured DLC coating. Lower graphitization in the case of textured DLC might be due to the wear particle capturing and lubricant retention ability of textures.
I. INTRODUCTION
Improving the tribological performance of contacting surfaces by texturing is a relatively new technique. Surface texturing has proven to reduce friction,1–4 wear and seizer.5 Various applications like piston/cylinder,2,6 mechanical seals,7 and cutting tools8 have been textured to improve their tribological performance. Mechanisms by which micro/nano textures improve the tribological behavior mentioned in the literature are: increases the load carrying capacity through a hydrodynamic effect, reduces third body abrasion by trapping wear particles, provides lubricant in mixed lubrication regime by acting as a second lubrication source and reduces the rise in temperature at contact by keeping the lubricant at the interface.9–12 In the last few years, effects of surface texturing have been investigated on diamond-like carbon (DLC) coated surfaces in oil-lubricated13,14 sliding conditions. DLC coatings are increasingly being used to improve the tribological performance of engineering components like bearings, gears, seals, metal cutting, and forming tools, magnetic hard disks and biomedical, due to their hardness and excellent mechanical and tribological properties.15 Because of the higher tribological performance, the use of DLC in automotive components is also increasing. The performance of DLC coating is influenced by Contributing Editor: Mohd Fadzli Bin Abdollah a) Address all correspondence to these authors. e-mail: [email protected], [email protected] DOI: 10.1557/jmr.2016.12 J. Mater. Res., 2016
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temperature, relative humidity etc. As automotive components are subject to higher temperatures, loads, and oxidative environments, to maintain the performance of DLC at these harsh conditions, DLC is doped with hydrogen, various metals, nitrides, and carbides.16 Surface texturing has recently been considered as one of the methods to maintain and enhance the tribological performance of DLC
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