Journal of University of Science and Technology Beijing
Volume 14, Number 2, April 2007, Page 167
Corresponding author: Shen-Jenn Hwang, E-mail: Hwang6@sunws.nfu.edu.tw Also available online at www.sciencedirect.com
Materials
Tribological properties of electroless Ni-P-SiC composite coatings
in rolling/sliding contact under boundary lubrication
Wei-Long Liu
1)
, Shu-Hue Hsieh
1)
, Shen-Jenn Hwang
2)
, Ting-Kan Tsai
1)
, and Wen-Jauh Chen
3)
1) Department of Materials Science and Engineering, Formosa University, Huwei, China Taipei
2) Department of Mechanical Design Engineering, Formosa University, Huwei, China Taipei
3) Department of Materials Engineering, Pingtung University of Science and Technology, Pingtung, China Taipei
(Received 2006-06-16)
Abstract: Ni-P-SiC composite coatings were prepared under a given bath composition and operation parameters of electroless plating.
The tribological properties of the Ni-P-SiC composite coatings after annealing at 400C for 1 h were tested in rolling/sliding contact
under boundary lubrication condition using a two-roller tribometer. The measurement contained friction coefficient, contact surface
temperature, contact electrical resistance, and wear rate of the Ni-P-SiC composite coatings under various slide to roll ratios, loads, and
rolling speeds. For the simultaneous examination of the effect of the chosen parameters on the tribological properties of the Ni-P-SiC
composite coatings, an orthogonal regression experimental design method was used.
Key words: Ni-P-SiC composite coating; rolling-sliding; friction; wear; two-roller test
1. Introduction
Composite coatings are a class of materials which
are mostly used for mechanical and tribological ap-
plications. The Ni-SiC composite coatings combine
anti-corrosion property because of the presence of Ni
with mechanical and tribological performance because
of the presence of SiC. The Ni-SiC composite coatings
can be made by electrolytic plating [1-10] or electroless
plating [11-20]. The coating by electroless plating can
possess different properties from electrolytic plating by
adjusting P content, crystal structure, and microstruc-
ture of coating.
The rate of incorporation of SiC into the Ni matrix is
roughly proportional to its concentration in the elec-
trolyte. The incorporation of SiC into Ni is also go-
verned by the degree of particle dispersion in solution,
mass transport, adhesion to the growing surface, and
the electro-crystallization of Ni around the SiC [17].
The number density of SiC in the coating increases
with decreasing particle size [8]. The addition of ultra
fine SiC particles into the Ni matrix apparently reduces
the size of Ni grains during the plating process and in-
hibits the grain growth during heat treatment [4-5]. The
hardness of the coating increases with the increase of
the SiC content in the coating and the wear resistance
increases to a maximum and then reduces again with
the increase of the size of the SiC particles in the
coating [5, 8, 18].
The hardness and wear resistance of composite
coatings can be markedly increased by heat treatment
[12], and the Ni-P-SiC composite coating kept at
400
C for 1 h has the highest hardness and wear re-
sistance [7, 13, 15].
Most tribological tests for composite coatings were
carried out in dry or lubricant condition using a ball on
disk tribometer. This kind of test can only evaluate the
performance of the device with reciprocating move-
ment, such as pistons. In this study, the Ni-P-SiC
composite coatings were first made under a given bath
composition and operation parameters of electroless
plating. Then the tribological properties of this
Ni-P-SiC composite coating were tested in roll-
ing/sliding contact under boundary lubrication condi-
tion using a two-roller tribometer. This test method can
really estimate the performance of the device with ro-
tary motion, such as bearings and gears.
2. Experimental
In this study, the measurement of tribological prop-
erties of electroless Ni-P-SiC composite coatings was
carried out in rolling/sliding contact under boundary
lubrication condition with two rollers. Both rollers
were made of quenched-and-tempered bearing steel
(AISI52100) and with a hardness of HRC 60
-62. After