Study on Microstructure and Tribological Properties of Oxygen Doped (VAlTiCrW)O_x High-Entropy Alloy Coatings

Abstract

Nonmetal doped high-entropy alloys have excellent mechanical properties，wear resistance and corrosion resistance，but there is still much room for improvement friction properties in high temperature.It is expected to achieve low friction through utilizing the characteristics of high-entropy alloys，when they are applied to high temperature working moving parts.In this work，(VAlTiCrW)Oxhigh-entropy alloy coatings with various oxygen content were prepared on the substrate surface by magnetron sputtering.The microstructure and tribological properties of the coating were evaluated by scanning electron microscope，atomic force microscope，X-ray diffractometer，high temperature friction testing machine，surface profiler，3D optical profiler and Raman spectroscopy.Results showed that with the increase of oxygen content，the coating structure gradually changed from BCC to indefinite amorphous structure，the hardness of the coating increased from 3.3 GPa to 11.9 GPa，and the elastic modulus increased from 97.92G Pa to 181.70 GPa.The average friction coefficient of the coating decreased from 0.49 to 0.39 at 700 ℃，but the wear rateincreased from 1.97× 10-5mm3/(N·m) to 6.41×10-4mm3/(N·m).Moreover，lowfriction coefficientresultedfrom the fact that oxygen doped coatings were more likely to form V2O5with lubricating effect at high temperatures，and correspondingly the wear rate of the coating increases due to the softening effect of V2O5.

Keywords

• oxygen doping；high-entropy alloy；high temperature friction；mechanical property