Abstract
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.
Highlights
The Cr+ ions were the main species in the HiPIMS plasma, while the neutral Cr and N occupied the species in the direct current magnetron sputtering (DCMS) plasma
It is believed that the ionic reaction between Cr+ and N+ during the coating growth in HiPIMS was the major reason for the superior properties of Chromium nitride (CrN) films
The ionic reaction led to the CrN film prepared by HiPIMS preferentially growing on the (200) plane rather than on the (111) plane in the film prepared by DCMS, but the microstructure was more compact
Summary
Chromium nitride (CrN) coatings consistently demonstrate high hardness, good toughness and wear resistance, and good corrosion resistance, having broad market prospects in the fields of cutting tools, engine parts, surface corrosion resistance, and surface decoration. At present, lots of fabrication methods have been employed in the preparation of CrN thin films, such as multiarc ion plating, reactive ion plating, hollow cathode discharge, and magnetron sputtering. Among them, magnetron sputtering is a lowtemperature technique with a high deposition rate process, which has received much more attention in the industry. For example, the direct current magnetron sputtering (DCMS) is widely used to prepare a smooth surface of CrN thin films as an anticorrosion layer. the application of CrN thin films prepared by DCMS is still limited by relatively small hardness, loose structure, and low adhesion.. The direct current magnetron sputtering (DCMS) is widely used to prepare a smooth surface of CrN thin films as an anticorrosion layer.. The application of CrN thin films prepared by DCMS is still limited by relatively small hardness, loose structure, and low adhesion.. The average free path of electrons is about 1 cm or less, and the pulsed power is 2–3 orders of magnitude higher than that in DCMS This technique is suitable for the preparation of dense and hard coatings. Greczynski et al. compared the influence of the O2/Ar ratio on the deposition rate and the crystal structure of CrN films prepared by DC and HiPIMS. We compare the relationship between the structure and mechanical properties of CrN films deposited by DCMS and HiPIMS, mainly emphasizing the anticorrosion property of coatings. It is believed that this work shall provide theoretical and experimental guidance for the application of HiPIMS in thin film depositions
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