Microstructure and mechanical properties of vanadium carbide coatings synthesized by reactive magnetron sputtering

Vanadium carbide coatings with different carbon contents were synthesized in Ar-C2H2 mixture by reactive magnetron sputtering. Energy-dispersive X-ray analysis, X-ray diffraction analysis, scanning electron microscopy, atomic force microscopy and nanoindentation were employed to investigate the effect of C2H2 partial pressure on the composition, phase, microstructure and mechanical properties of the coatings. The results show that vanadium carbide coatings can be synthesized at a low partial pressure of C2H2. The c-VC coating with columnar crystal is obtained when the proportion of C2H2 partial pressure is only ∼3% in the mixture. It reaches the peak hardness of 35.5 GPa and elastic modulus of 358 GPa, respectively. The presence of excessive carbon with increased C2H2 partial pressure in the h-VC coating leads to the significant decrease of hardness and elastic modulus.