Journal of University of Science and Technology Beijing
Volume 14, Number 4, August 2007, Page 1
Corresponding author: Guangneng Dong, E-mail: donggn@mail.xjtu.edu.cn Also available online at www.sciencedirect.com
Materials
Tribological behaviors of spot-textured TiN coatings on M2 high-speed
steel under boundary lubricated conditions
Guangneng Dong
1)
, Meng Hua
2)
, Jian Li
3)
, H.Y. Ma
2)
, and Youbai Xie
1)
1) Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jioatong Univer-
sity, Xi’an 710049, China
2) Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Kowloon,
Hong Kong
3) Wuhan Research Institute of Materials Protection, Wuhan 430030, China
(Received 2006-11-08)
Abstract: The effect of sliding durations on the tribological behaviors of spot patterned coatings was investigated. Two patterns
based on physical vapor deposition (PVD) TiN coatings were used such as in-lined (IN) and staggered (ST) spots. The tribological
behaviors were evaluated by a Cameron-Plint wear test rig. The M2 steel discs deposited TiN coatings with IN and ST patterns slid
against ASSAB 17 tool steel pins at a speed of 0.23 m/s, in Shell Tellus T32 lubricant and loaded with 900 N. The testing results on
disc specimens with the two types of PVD TiN spots patterns, all coated with a bias voltage of 180 V and respectively slid for 4, 8
and 11 h, were presented. The results revealed that the in-lined coatings possessed relatively better wear behaviors than the staggered
pattern coatings. Mechanisms for such superiority and for the causes of peeling were discussed. Relevant design approach was sug-
gested for the application of such patterned coatings.
Key words: vapor deposited coating; texture; friction; wear; boundary lubrication
[This study was financially supported by the National Natural Science Foundation of China (No. 50575173).]
1
. Introduction
Under mixed lubrication conditions, texture orien-
tation on the substrate has an effect on load-bearing
capacities. This texture orientation can be described
with an aspect ratio γ of length-to-width, generally
known as an orientation index [1]. The transverse
island surface texture with γ < 1 generally enhances
the load-bearing capacity and produces low friction
[2]. Obviously, controlled surface textures such as
micro-pits, protuberances and depressions/troughs
etc. can improve the tribological properties of a slid-
ing surface. The mechanism of textures depends on
contact situations. In full film lubrication the textures
can increase the hydrodynamic effect of lubricant [3].
In boundary lubrication textures can act as reservoirs
to supply lubricant inside the contact even during
sliding [4]. In dry and also sometimes in boundary
lubricated cases textures can trap wear particles and
thus the adhering and deformation components of
friction can be reduced and the lifetime increases [5].
The results showed that different micro-pits and
pores on two sliding surfaces such as a cylinder vs.
piston rings [6] yielded different lubrication condi-
tions. The loss of an internal combustion engine is
reduced by 2.0%-2.6% as a result of micro-pits at the
surface of piston skirt with the depth of a few mi-
crometers
[7].
Physical vapor deposition (PVD) TiN coatings are
widely used in improving tribological properties of
mechanical components such as high-speed steel cut-
ting tools. There are some evidences for TiN/CrN
multilayered coating to show longer life in drilling
testing [8]. Researches of TiN coatings [9-10] have
shown that PVD TiN coating minimizes wear loss
and diminishes failure of components. The surface
patterned with spotted PVD TiN coating might inte-
grate the advantage to the formation of hydrodynam-
ic effect [11-12] with the wettability of coatings [13]
under lubricated conditions. Preliminary study on
tribological behaviors of some PVD TiN patterns on
M2 steel was thus conducted [14]. The results
showed that the tribological behaviors for the
in-lined (IN) and staggered (ST) PVD TiN spot