Synthesis, microstructural characterization and nanoindentation of Zr, Zr-nitride and Zr-carbonitride coatings deposited using magnetron sputtering

Introduction: Hard coatings are primarily based on carbides, nitrides and carbonitrides of transition metal elements such as W, Ti, Zr, etc. Zr-based hard coatings show good resistance to wear, erosion, and corrosion as well as exhibit high hardness, high temperature stability, and biocompatibility, making them suitable candidates for tribological, biomedical, and electrical applications. Objectives: The present study aims to synthesize uniform and adherent hard Zr-based coatings that demonstrate sound mechanical integrity. Methods: Stainless steel (SS316) samples were coated with single layers of Zr, Zr-nitride, and Zr-carbonitride using magnetron sputter deposition technique. Deposition conditions were controlled to produce each coating with two different thickness i.e., 2 and 3 μm. Calotest was employed to confirm coatings thickness. Scanning electron microscope fitted with energy dispersive x-ray spectrometer was used to ascertain the morphology and elemental constitution of coatings. Cross-sectional samples were examined to ascertain coatings thickness and adhesion. X-ray diffractometer was employed for structural analysis. Instrumented nanoindentation hardness and elastic modulus were determined with nanoindenter. Ratio of nanohardness to elastic modulus was evaluated to observe the effect of coatings thickness on tribological behavior. Results: Three coating compositions were produced namely hcp-Zr, fcc-ZrN and fcc-Zr₂CN. The highest hardness and elastic modulus were shown by ZrN coatings while pure Zr coatings showed the lowest values. Conclusion: All coating compositions were found to be relatively uniform, continuous and adherent with no evidence of decohesion at the coating-substrate interface. Coatings produced in this study are thought to be suitable for tribological applications.