Effect of TiN, TiAlCN, AlCrN, and AlTiN ceramic coatings on corrosion behavior of tungsten carbide tool

Hard ceramic coatings are widely used for cutting and forming applications because these coatings on the surface of the tools considerably improve the oxidation, wear, and corrosion resistance of the materials. The aim of this study is to investigate the electrochemical corrosion behavior of TiN, TiAlCN, AlCrN, AlTiN, and multi-layered coat of AlTiN on tungsten carbide (WC) at different mediums. Coatings were performed using the cathodic arc evaporation-physical vapor deposition (CAE-PVD) method. The corrosion behaviors of the coated and uncoated WC materials were carried out with potentiodynamic polarization curves which used to calculate the corrosion rate of the tested materials at the pH values of 2, 7, and 10 at the room temperature. The surface morphologies of the uncoated and coated samples were examined by a scanning electron microscopy (SEM) before and after the corrosion testing. The corrosion experiment results indicated that the corrosion rate (114.7 x 10-6 mpy) of TiAlCN coating was much lower than WC substrate material (38.83 mpy) in pH = 7. The highest corrosion rate (1.559 mpy) was obtained for TiN coating, although the corrosion rate (490.8 x 10-9 mpy) of AlCrN coating was lower in pH = 10. The corrosion resistance of AlCrN coating was also the highest, even if in acidic environment.