Optimization of chromium nitride (CrNx) interlayers for hydrogenated amorphous carbon (a-C:H) film systems with respect to the corrosion protection properties by high power impulse magnetron sputtering (HiPIMS)

Abstract

Abstract Chromium nitride (CrN x ) films are frequently used as interlayers to enhance the adhesion of hydrogenated amorphous carbon (a-C:H) films on steel substrates. The microstructure of these CrN x interlayers has a direct influence on the corrosion protection properties of the a-C:H films. A dense and defect-free microstructure can improve the corrosion resistance. In this study, chromium nitride (CrN x ) films were optimized by high power impulse magnetron sputtering (HiPIMS) in order to reduce the film defect density. The HiPIMS-CrN x films were deposited on polished AISI 52100 (100Cr6) steel shims with a hardness of 60 ± 2 HRC using a Cemecon CC800®/9 HiPIMS device. The influence of the cathode pulse duration, cathode frequency and bias pulse duration on the deposition rate, nitrogen content, phase composition, microstructure and mechanical properties of CrN x films were investigated by glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), electron microscopy and microhardness measurements. Additionally, the corrosion resistance of HiPIMS-CrN x /a-C:H-coated 100Cr6 steel shims was tested by neutral salt spray test. For lower duty cycles an enhanced corrosion protection was observed due to a densification of the CrN x film microstructure and a decrease of the film defect density.