Oxidation of The Arc Ion-plated CrN Coatings at Elevated Temperatures

摘要

Characterization of the CrN coatings oxidized in air at temperatures ranging from 300 deg C to 800 deg C for 60 mm was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The CrN coatings were prepared by cathodic arc ion plating deposition on a type 304 stainless steel with a Cr interlayer. The XRD results show that oxidation of the CrN-coaled steel above 500 deg C produces two new phases, Cr_2O_3 and beta-Cr_2N, and the amount of both phases increases with the oxidation temperature. A noticeable change in the surface morphology of the coatings were observed by SEM in the specimens oxidized at temperature above 600 deg C. Cross-section TEM reveals that oxidation of the CrN-coated steel at high temperatures produces an oxide layer, Cr_2O_3, on the coating surface, and the underlayer is a mixture of CrN and beta-Cr_2N phases. Unlike the as-deposited specimen, the dual phase layer in the oxidized specimens has an equiaxed grain structure and the average grain size of the layer increases with the oxidation temperature. Depth profiling of the oxidized CrN coatings at various temperatures by AES gives the elemental distributions near the free surface, and the activation energy for oxidation of the CrN coatings was calculated to be 1.63 eV