Effect of Ni addition on the structure and properties of Cr-Ni-N coatings deposited by closed-field unbalanced magnetron sputtering ion plating

Closed-field unbalanced magnetron sputtering ion plating (CFUMSIP) is a versatile technique for the preparation of high-quality coatings due to the enhancement of plasma density during deposition. In this study, Cr-Ni-N hard coatings with different Ni contents (0-64at.%) were deposited onto AISI M2 steel substrates by CFUMSIP in Ar-N₂ reactive gas mixtures. The coatings were characterized in terms of their structure and properties by a variety of techniques, such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), micro-indentation, reciprocating wear tester, etc. The surface free energy of the coatings was calculated using the Owens-Wendt geometric mean approach. The experimental results indicated that the microstructure and properties of Cr-Ni-N coatings changed with the incorporation of Ni content at different level. The resultant Cr-Ni-N coatings were consisted of Cr₂N, CrN and metallic Ni mixed phases. With the appropriate addition of Ni in the range of 20-40at.%, the fracture toughness and wear resistance could be improved as compared to the Cr-N binary coating, and the hardness remained relatively high (20-23GPa). Additionally, both low total surface energy (18-22mN/m) and low polar component of surface energy (0.1-0.2mN/m) could be obtained in the Cr-Ni-N coating system. Therefore, the Ni incorporation can provide an effective route to tailor the structure and properties of the Cr-Ni-N coatings. The good combined properties of the Cr-Ni-N coatings demonstrate their potential for applications in plastic injection molding. © 2012 Elsevier B.V.