Impact of sputtering gas on the microstructural, mechanical and wetting properties of vanadium nitride coatings

Abstract

Vanadium nitride (VN) coatings were deposited via reactive DC magnetron sputtering technique on a hot substrate (400 degrees C) with varying partial pressure of N2. The impact of nitrogen partial pressure on the crystal structure, microstructure, elemental composition, surface topography, mechanical and wetting properties of VN coatings was investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS), atomic force microscope (AFM), nano-indentation, and drop shape analyzer (DSA). The variation in the N2 partial pressure leads the significant changes in the microstructure, mechanical, and wetting properties of the coatings. The GIXRD spectra reveal the formation of crystalline FCC phase in the deposited VN coatings. However, at 100% N2 partial pressure, the preferred orientation of crystal planes changes from (200) to (220). The FESEM image reveals that at low N2 partial pressure, the coating exhibits well-separated grains with clearly visible grain boundaries. As the N2 partial pressure increases, the agglomeration of grains becomes more pronounced, and the grain boundaries become less discernible. However, at 100% N2 partial pressure, the structure transforms into triangular nanoflake-like prismatic structures with voids. The VN coatings with 60% N2 partial pressure exhibit the highest mechanical properties whereas at 100% N2 partial pressure, the VN coatings reveal a super-hydrophilic character.