Low friction in self-mated silicon carbide tribosystem using nanodiamond as lubricating additive in water
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Low friction in self-mated silicon carbide tribosystem using nanodiamond as lubricating additive in water Xudong WANG1,2, Hirotsuna SATO2,3, Koshi ADACHI2,* 1
Université Paris-Saclay, UVSQ, LISV, Vélizy–Villacoublay 78124, France
2
Department of Mechanical Systems Engineering, Graduate School of Engineering, Tohoku University, 6-6-01, Aramaki-azaAoba, Aoba-ku, Sendai 980-8579, Japan
3
Hino Motors, Ltd., 3-1-1, Hino-dai, Hino-shi, Tokyo 191-8660, Japan
Received: 27 February 2020 / Revised: 18 May 2020 / Accepted: 28 June 2020
© The author(s) 2020. Abstract: Nanodiamond particles (NDPs) have been considered as a potential lubricant additive to various tribological applications, such as water lubrication systems. In this study, the tribological properties of silicon carbide (SiC) lubricated by NDPs dispersed in water are investigated utilizing the ball-on-disk tribometer. It is found that the slight addition of NDP to water (i.e., 0.001 wt%) can distinctly accelerate the running-in process, which is necessary to achieve a friction coefficient (μ) as low as 0.01. This study also discusses two NDP functional terminations—hydroxyl and carboxyl. It is demonstrated that the use of carboxyl-terminated NDP over a wide range of concentration (0.001 wt%–1 wt%) yields a low friction force. In contrast, the ideal effective concentration of hydroxyl-terminated NDP is considerably limited because agglomeration in this material is more probable to occur than in the former. Meanwhile, when utilizing NDPs, the input friction energy ( Pin , defined as the product of sliding speed and applied load) is found to have an essential function. Several sliding tests were implemented at various Pin values (50– 1,500 mW) using carboxyl-terminated water-dispersed NDPs. It was observed that the μ and wear decreased with increasing Pin when 200 mW < Pin < 1,500 mW. However, when Pin < 200 mW, low friction with high wear occurs compared with the resulting friction and wear when pure water is used. Keywords: nanodiamond particle; silicon carbide (SiC); lubrication; termination groups; running-in; driving energy
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Introduction
Since the 1980s, low viscosity and environmentally friendly water has been investigated as a potential lubricant to improve the tribological performance of ceramics [1–6]. Silicon carbide (SiC), which is one of the most widely used antifriction materials, is a typical representative ceramic. Chen et al. [7] have reported that the sliding friction in self-mated SiC gradually decreases in the presence of water. In other words, running-in is required to achieve
low friction in water. It has also been demonstrated that the rougher the SiC surface, the longer the required running-in period [8]. The effect of running-in is explained from the viewpoint of wear, and it has been recognized that the chemical wear of SiC in water is extremely important. However, the hydrothermal oxidation of SiC requires high pressure and high temperature. The chemical reactions indicate that the
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