Ultra-low friction properties of carbon nitride tantalum coatings in the atmosphere

• The CNx:Ta coating showed ultra-low friction in the atmosphere.
• The XPS analysis revealed the chemical composition of the CNx:Ta coating, which had TaC and TaNx bonds.
• The oxygen desorption from the CNx:Ta coating was determined by AES analysis.

In this research, a tantalum (Ta) addition to the Carbon Nitride (CNx) coating was focused on to obtain its high hardness and a low-friction coefficient by varying the graphite-like structure at the topmost surface. A CNx:Ta coating was synthesized by a co-sputtering technique with tantalum set on a carbon target, and then XPS analysis was conducted for a better understanding of chemical bonding. The friction test was conducted in the atmosphere, and basic mechanical property of hardness was measured by Nanoindentation hardness tester. The XPS analysis revealed that TaC and TaNx in the coating bonded with some sort of oxygen and also TaC and TaNx did not strongly interact with the carbon structure. The friction coefficient of CN0.22:Ta was observed to be 0.01–0.02 with a built-up transfer layer on the counter material′s surface.