RF magnetron sputtered Nb-V-N composite coatings for high-temperature self-lubricant applications

Enhancing the tribological properties of hard ceramic coatings for high temperature applications is one of the hot topics in the solid lubricant field. In this paper, a series of Nb-V-N coatings with different V concentrations were deposited using RF magnetron sputtering system, and the crystalline structure, mechanical and tribological properties were investigated. Results showed that the Nb-V-N coatings regardless of V concentrations exhibited two phase fcc-NbN with V in solid solution and hcp-NbN phase. The hardness and elastic modulus of the coatings were enhanced by adding 5.3 at.% of V. The room temperature tribological properties of the coatings were improved by the addition of V well due to the enhanced mechanical properties and the nature excellent self-lubricant characteristics. The evaluation of main tribophase from the wear track at elevated temperatures from the self-lubricant V2O3 at 400 degrees C to the V2O5 at 800 degrees C, contributed to the stable and excellent anti-frictional properties of the coating with a V concentration of 12.4 at.%. However, the wear rate of the coatings drops gradually with the increase of V concentrations due to the large amount of soft but lubricant tribophases at elevated temperatures.