The superior properties of CrN coatings prepared by high power pulsed reactive magnetron sputtering

In this paper, we investigate the properties of chromium nitride (CrN) coating prepared using a high power magnetron sputtering (HiPIMS) technique. As a comparison, CrN coating prepared using a direct current magnetron sputtering (DCMS) technique is also studied. The crystal structure, surface and cross-sectional morphologies, and composite properties of the as-deposited CrN coatings are compared by x-ray diffraction, a scanning electron microscope, and a microhardness tester, respectively. It is found that the as-deposited CrN film by HiPIMS grew preferentially on (200) facet when compared with that by DCMS on (111) facet. As a result, the coatings deposited by HiPIMS have a very compact microstructure with high hardness: the microhardness reached 855.9 Hv replacing 501.5 Hv by DCMS. Besides, the inner-stress of CrN films prepared by HiPIMS is also relatively small. After measuring the corrosion resistance, the corrosion current of films prepared by HiPIMS was an order of magnitude smaller than that of CrN films deposited by DCMS. Based on the plasma diagnostics by time resolved optical emission spectroscopy, it is believed that the superior quality of CrN coatings prepared by HiPIMS is because of the ionic reaction between Cr+ and N+, rather than the neutral Cr and N reaction in DCMS during the CrN film growth.