Influence of Wettability and Mechanical Properties on Tribological Performance of DLC Coatings under Water Lubrication

Chaoqun Zhang,Masahiro Fujii

doi:10.4236/jsemat.2015.53013

Chaoqun Zhang, Masahiro Fujii

Open Access

https://doi.org/10.4236/jsemat.2015.53013

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Abstract

DLC coatings are currently used in a wide variety of industrial fields because of their outstanding properties such as high hardness, high wear resistance, low friction and so on under oil lubrication as well as no lubrication. In order to evaluate the tribological performance of DLC coatings under water lubrication, eight types of DLC coatings were evaluated by water-lubricated sliding tests at sliding velocities of 0.02 m/s and 0.1 m/s. The different DLC coating types comprised both hydrogenated and hydrogen-free DLC films that were deposited using different techniques: amorphous hydrogenated DLC (a-C:H), that doped with tungsten (a-C:H:W), that doped with silicon (a-C:H:Si) and hydrogen-free DLC (ta-C). DLC coatings showed low friction coefficient and excellent wear resistance. Friction coefficient and wear rate decreased with increasing sliding velocity. The effect of surface wettability and mechanical properties on tribological characteristics was investigated. Friction coefficient decreased as the contact angle increased. Hydrogen-free DLC coating with the highest hardness showed the highest friction and a larger wear rate. Furthermore, DLC coatings deposited with interlayer showed longer lifetimes.

Highlights

Water lubrication system is a candidate of a substitution for conventional oil lubrication systems to resolve the environment pollution of oil lubricant
DLC-4 deposited by multiple methods of physical vapor deposition (PVD) and chemical vapor deposition (CVD) doped with some silicon showed a low friction coefficient (0.10 - 0.25) in sliding velocity of 0.02 m/s, and showed a lower and a steady friction coefficient (0.05 0.15) in sliding velocity of 0.1m/s
We investigated the effect ofwettability on friction coefficient and wear rate of DLC coatings under water lubrication

Summary

Introduction

Water lubrication system is a candidate of a substitution for conventional oil lubrication systems to resolve the environment pollution of oil lubricant. The conventional use of oil lubrication systems in equipment has some disadvantages of environmental damage from leakage, risk of fire, and environmental load. (2015) Influence of Wettability and Mechanical Properties on Tribological Performance of DLC Coatings under Water Lubrication. Fujii tion systems could eliminate these disadvantages, they have tribological problems such as high friction and wear due to the low lubricating propertiy [1]-[3]. The corrosion induced by water would restrict the application of metallic materials in the water lubrication systems. From the viewpoint of environmental protection, it is desirable to use water without additives, such as corrosion inhibitors, lubricating additives, and so on. An alternative approach is to take advantage of the metallic materials modified with depositing hard coatings with good lubricity in water environment [4]

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