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

Abstract

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.