TITLE:
Influence of Wettability and Mechanical Properties on Tribological Performance of DLC Coatings under Water Lubrication
AUTHORS:
Chaoqun Zhang, Masahiro Fujii
KEYWORDS:
DLC, Friction, Wettability, Hardness, Water Lubrication
JOURNAL NAME:
Journal of Surface Engineered Materials and Advanced Technology,
Vol.5 No.3,
June
8,
2015
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.