Effect of Temperature on Corrosion Resistance and Passive Film Properties of TiAlCN Coatings

Mechanical parts are easy to fail under the action of high temperature and corrosion environment, physical vapor deposition coatings can be used to improve the surface performance of these parts and increase their service life. The corrosion resistance of coatings is related to their passivation performance. Thereinto, the temperature plays a key role in the passivation performance of the materials, thus tuning their corrosion rate. This work studies the change of corrosion resistance of TiAlCN coatings in the 3.5 wt.% NaCl solution at various temperature and further reveals the mechanism that how the temperature affects the corrosion resistance and passive film properties. Based on the cathode arc technique, a TiAlCN coating was deposited on a 316 stainless steel substrate with a dimension of ϕ8 mm×10 mm. In order to improve the binding force between the coating and the substrate, the coating was designed into a composite structure, and the bottom layer TiN and the transition layer TiAlN were successively deposited between the outer layer TiAlCN and the substrate. The micromorphology and phase constituent of the coating were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectrometer (XPS). Open circuit potential, electrochemical impedance spectroscopy (EIS), dynamic potentiodynamic polarization, potentiostatic polarization and Mott-Schottky tests were carried out on the coating with platinum electrode as auxiliary electrode and saturated silver chloride electrode as reference electrode in 3.5wt.% NaCl solution by electrochemical workstation. The corrosion behavior of the coating and semiconducting properties of the passive film at different temperature (20, 40, 60, 80 ℃) were studied. Among them, the polarization potential of the potentiostatic polarizations was selected in the passivation interval of the dynamic potential polarization curve. In the electrochemical experiment, the water bath crucible was utilized to maintain the electrolyte at the corresponding polarization temperature. In addition, X-ray photoelectron spectrometer was adopted to characterize the chemical distribution of the passive film formed on the TiAlCN coating. There were pits, particles and pinholes on the surface of the TiAlCN coating, with a typical columnar crystal structure. In addition, the coating was in a face-centered cubic structure, which composed of TiC and TiN phases. Meanwhile, the corrosion current density and the passivation current density increased, and the diameter of capacitive arc decreased, and the corrosion resistance of the coating decreased with the increase of temperature. The pitting potential of 316 stainless steel and the TiAlCN coating decreased with the increase of temperature, indicated that the pitting sensitivity of both increased. Meanwhile, the main components of the passive film were Al2O3 and TiO2, which decreased with the increase of temperature. As the temperature raised from 20 ℃ to 80 ℃, the passive film of the TiAlCN coating exhibited n-type semiconducting properties. Also, the donor density of the passive film increased from 1.14×1016 cm−3 to 3.27×1016 cm−3, indicated that the defects of the passive film increased, which was conducive to the erosion of corrosive ions, resulting in the worst protection ability of the passive film. Consequently, high temperature has a significant effect on the corrosion resistance of TiAlCN coatings by loosening the passive film and increasing the carrier density, which worsens the protectiveness of the passive film and the anti-corrosion capacity of the coating. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.