Influence of silicon on the microstructure and the chemical properties of nanostructured ZrN-Si coatings deposited by means of pulsed-DC reactive magnetron sputtering

Transition metal nitride coatings have been widely used in various industrial applications due to their physical and chemical properties. For instance, they have been used as protective coatings against wear and corrosion. Among the large family of metal nitride coatings, zirconium nitride (ZrN) has been extensively studied in order to determine its suitability for different applications, due to the fact that ZrN coatings have been shown to have better corrosion resistance, lower resistivity, and higher mechanical properties than titanium nitride (TiN) coatings. In this investigation, ZrN coatings with different silicon (Si) contents were deposited by means of pulsed-DC reactive magnetron sputtering, and the influence of the Si content on the composition, chemical state of the elements, microstructure, and optical and electrochemical properties of the coatings was studied using energy-disperse spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), UV-vis-IR spectrophotometry, and a Gamry 600 potentiostat at room temperature. The results showed that ZrN coatings are nanostructured with a fcc structure, are polycrystalline, and have a mixture of columnar and grained morphology. The incorporation of Si causes a decrease in the coating's crystallinity, characterized by a decrease in the intensity and a broadening of the XRD peak, attaining amorphous-like behavior as the Si content increases. The morphology of cross-sectional of the ZrN coatings with silicon tends to a featureless arrangement, coherent with the grain refinement that is generated by the Si incorporation. The XPS results show the presence of oxygen on the surface of the coatings, generating a mixture of phases of ZrN, ZrON and ZrO2. The optical results show that the addition of Si promotes the formation of transparent coatings, due to the formation of a SiNx phase, while the electrochemical results show that with the addition of Si, the corrosion resistance of the substrate improves.