Effect of bias voltages on microstructure and properties of (TiVCrNbSiTaBY)N high entropy alloy nitride coatings deposited by RF magnetron sputtering

Abstract

(TiVCrNbSiTaBY)N high entropy alloy nitride (HEAN) coatings have been deposited onto Si (100) and cemented carbide substrates by radio frequency magnetron sputtering. The deposition is carried out at different bias voltages to study its influence on microstructure, morphology, mechanical properties and tribological behaviour of the coatings. Grazing Incidence X-Ray Diffraction (GIXRD) technique shows that all coatings exhibit single NaCl-type face-centered cubic (FCC) crystal structure, while the preferred orientation of the crystal structure is greatly affected by the bias voltages. High resolution transmission electron microscopy (TEM) reveals that the structure of the coatings is a mixture of amorphous-like phase and FCC crystal structure, which is in agreement with GIXRD data. Cross-sectional Scanning Electron Microscopy (SEM) images exhibit that the columnar structure of the coatings gradually transforms into a featureless dense structure with the increase of bias voltage. SEM and Atomic Force Microscopy reveal that the surface morphology become smoother with increasing bias voltage. The (TiVCrNbSiTaBY)N HEAN coating deposited at a specific bias voltage exhibit a high hardness of 32.2 GPa. The friction coefficient is significantly influenced by the variation of the coatings surface roughness. Tribological tests for coating deposited without and at low bias voltage show that the wear behavior of the coatings is severe abrasive wear and adhesive wear, while at high bias voltage the slight abrasive wear appears. By applying the substrate bias voltage, the (TiVCrNbSiTaBY)N coatings exhibit excellent mechanical and tribological performance, which can be a promising candidate for protective coating in cutting tools or components.