| AVS 63rd International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+BI+SE+TF-ThA |
| Session: | Materials Tribology |
| Presenter: | Masao Noma, Shinko Seiki Co., Ltd, Japan |
| Authors: | M. Noma, Shinko Seiki Co., Ltd, Japan K. Eriguchi, Kyoto University, Japan M. Yamashita, Hyogo Prefectural Institute of Technology, Japan S. Hasegawa, Osaka University, Japan |
| Correspondent: | Click to Email |
Solid lubricant material with low friction coefficient is of technological interest for its usage under harsh environments such as ultra-high vacuum. At present, MoSi -containing films [1] are the most widely employed for space applications because of their low friction coefficients (0.02–0.05) in vacuum [2]. However, the mechanical hardness and the oxidation resistance temperature are 10–20 GPa [3] and 360 °C [4], respectively, inapplicable to a long term operation in space. Boron nitride (BN) films have been considered an alternative material because of their superior high hardness and oxidation resistance temperature, 45 GPa and 1200 °C, respectively [5]. We have proposed a novel reactive plasma-assisted coating technique (RePAC) for forming 1-μm-thick high-hardness BN films (~50 GPa) [6][7]. In this study, we present "friction coefficient lowering" phenomena in the high-hardness BN films under ultra-high vacuum (~10−6 Pa), which is in sharp contrast to "friction coefficient increase" usually observed for other hard coating materials. The time-dependent high-vacuum friction measurement revealed that the friction coefficient decrease from 0.1 to 0.03 was found for the substrate bias voltage from −90 to −180 V in the RePAC. In this (incident ion energy) region, the cubic BN phase was formed in the turbostratic BN background, leading to the high-hardness of ~50 GPa at atmosphere [7]. Moreover, the obtained low friction coefficient was confirmed to be stable (<0.05) for long time exposures to the vacuum (~96 hrs). The friction coefficients of the present BN films are comparable to widely reported values of MoS2 films. The BN film prepared by the RePAC is one of promising hard coating materials for harsh environment (e.g., space) applications.
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[5] C. B. Samantaray and R. N. Singh, Int. Mater. Rev.50 (2005) 313.
[6] M. Noma et al., Jpn. J. Appl. Phys.53 (2014) 03DB02.
[7] K. Eriguchi et al., AVS 61st Int. Symp. & Exhibition, SE+NS+TR-TuM3 (2014).