Effect of temperature and mating pair on tribological properties of DLC and GLC coatings under high pressure lubricated
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Effect of temperature and mating pair on tribological properties of DLC and GLC coatings under high pressure lubricated by MoDTC and ZDDP Kang LIU1, Jia-jie KANG1,2,3,*, Guang-an ZHANG4,*, Zhi-bin LU4, Wen YUE1,2,3 1
School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China
2
Key Laboratory of Deep GeoDrilling Technology of Ministry of Natural Resources, Beijing 100083, China
3
Zhengzhou Institute, China University of Geosciences (Beijing), Zhengzhou 451283, China
4
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
Received: 02 March 2020 / Revised: 05 May 2020 / Accepted: 14 June 2020
© The author(s) 2020. Abstract: Diamond-like carbon (DLC) and graphite-like carbon (GLC) coatings have good prospects for improving the surface properties of engine parts. However, further understanding is needed on the effect of working conditions on tribological behaviors. In this study, GLC and two types of DLC coatings were deposited on GCr15 substrate for investigation. The friction and wear properties of self-mated and steel-mated pairs were evaluated. Two temperatures (25 and 90 ℃), three lubrication conditions (base oil, molybdenum dithiocarbamate (MoDTC)-containing oil, MoDTC+zinc dialkyldithiophosphate (ZDDP)containing oil), and high Hertz contact stress (2.41 GPa) were applied in the experiments. The results showed that high temperature promoted the effect of ZDDP on steel-mated pairs, but increased wear under base oil lubrication. The increased wear for steel-mated pairs lubricated by MoDTC-containing oil was due to abrasive wear probably caused by MoO3 and β-FeMoO4. It was also found that in most cases, the tribological properties of self-mated pairs were better than those of steel-mated pairs. Keywords: diamond-like carbon (DLC); graphite-like carbon (GLC); mating pair; temperature; oil additives
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Introduction
In recent years, the increased number of motor vehicles has made automobile exhaust emissions an issue of concern in the society. Excessive emissions not only cause severe air pollution but also energy waste and economic losses. To achieve the goal of energy conservation and emission reduction, the European Union has published emission standards, such as “Euro V” and “Euro VI” [1]. For passenger cars, approximately 28.8% of the energy generated by fuel is used to deal with unnecessary friction in components, such as the engine, whereas the energy
required to drive the car accounts for only 21.5% [2]. Thus, reducing the friction of transmission parts is a major challenge for improving fuel efficiency and reducing emission. Diamond-like carbon (DLC) coating possesses excellent friction reduction and wear resistance characteristics as well as good chemical inertness [3, 4]. Graphite-like carbon (GLC) coating is mainly comprised of highly disordered sp2 bonds with small graphite clusters [5] that exhibit good tribological propertie
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