Tribological properties of ta-CNx coating sliding against steel and sapphire in unlubricated condition

• Published in: Tribology international Vol. 131; pp. 102 - 111
• Main Authors: Liu, Xiaoxu, Umehara, Noritsugu, Tokoroyama, Takayuki, Murashima, Motoyuki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2019; Elsevier BV
• Subjects: Amorphous materials; Carbon nitride; Friction; Gas atmosphere; Graphitization; Humidity; Rare gases; Sapphire; Sliding; ta-CNx coating; Temperature; Tribological property; Tribology; Wear; Tribological property; Temperature; ta-CNx coating; Gas atmosphere
• ISSN: 0301-679X; 1879-2464
• DOI: 10.1016/j.triboint.2018.10.022

Tribo-behavior of tetrahedral amorphous carbon nitride (ta-CNx) coating in unlubricated condition was investigated in this study. Sliding against steel, low nitrogen content ta-CNx exhibits much lower friction and wear as temperature increases, with less adhesion wear than ta-C and remained relatively higher hardness (45.01 GPa). Nevertheless, against sapphire ta-C outperforms ta-CNx greatly, and graphitization could be found at 120 °C. With atmosphere humidity increasing, ta-CNx shows significantly decreased friction, implying the tribo-character of high sp3 bonding structure. Meanwhile, dry air seems to be the harshest condition for ta-CNx, since O2 in the atmosphere might lead to oxidized wear of ta-CNx even under room temperature. Furthermore, in humid N2, as an inert gas with high humidity, ta-CNx shows the lowest friction and wear. •Tribological properties of ta-CNx coating under unlubricated condition were studied.•As temperature rising ta-CNx shows distinct tribo-behavior against steel or sapphire.•Against steel low nitrogen ta-CNx shows lower friction and wear than ta-C over 50 °C.•Friction of ta-CNx was greatly affected by the humidity and oxygen in the atmosphere.