Hard nitride coatings with properties such as high chemical stability, good toughness, high hardness and adhesion, excellent corrosion and abrasion resistance are produced by physical vapor deposition method. In this study, TiN, CrN and ZrN coatings were coated as hard layers by cathodic arc vapor deposition on 420 stainless steel, H13 tool steel and Ck45 carbon steel substrates. In order to improve the microstructure and increase the hardness of the substrates, heat treatment cycles appropriate to each steel were carried out. X-ray diffraction (XRD) was employed to eva‎luate the crystal structure and grain size of the coatings. According to the results obtained from XRD analysis, CrN and Cr2N phases were identified in the chromium nitride coatings and the peaks of Cr2N had higher intensity in the Ck45 substrate. CrN coating on substrate 420 revealed smaller grain size. Coating thickness, surface morphology and wear tracks were examined by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The surface roughness of the samples was measured before and after the coating operation and it was found that the roughness increased after the coating due to the presence of macroparticles on the surface. Using Pull-off test and Rockwell C hardness test, the adhesion of the coating to the substrates was eva‎luated; it was found that the adhesion of the coating to the substrate is affected by surface roughness and TiN coating on substrate 420 showed the best adhesion behavior. The mechanical properties of the coatings were investigated by microhardness test and in order to eva‎luate the tribological behavior, the pin-on-disc wear tests were conducted to report the mean coefficient of friction and wear rate. CrN coating on the substrate 420 showed the lowest wear rate, but the highest wear rate belonged to ZrN coating on Ck45 substrate. Corrosion behavior of the specimens was eva‎luated by electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5% NaCl solution. Electrochemical impedance test showed that CrN coating, with lower roughness, less number of macroparticles and small holes on the surface, fine grain size and dense structure, showed better corrosion resistance than other coatings. Potentiodynamic polarization tests also proved the lower corrosion current density of the CrN coating over 420 substrate. Studies have shown that the presence of macroparticles and cavities on the surface strongly affects the amount of corrosion. ZrN coating on Ck45 substrate showed lower corrosion resistance. Based on the findings of this study, CrN coating on 420 substrate experiences the best performance and ZrN coating on Ck45 substrate proved the weakest behavior in terms of wear and corrosion.

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علي شفيعي، محمدرضا سليمي جزي