High Temperature Oxidation of Nickel-Based Cermet Coatings Composed of Al2O3 and TiO2 Nanosized Particles

The use of co-electrodeposited nickel-based cermet coatings has been recently considered as a low cost method for protecting the surface of mechanical equipment and machinery against corrosion and high temperature oxidation that are being used in a new oil extraction techniques known as the in situ combustion (ISC) process. In the ISC process, the presence of high temperature atmospheric air can degrade the surface of commercially alloyed components rapidly. This paper investigates the high-temperature oxidation behaviour of novel nanostructured cermet coatings composed of two types of dispersed nanosized ceramic particles (Al₂O₃ and TiO₂) in a nickel matrix and produced by co-electrodeposition technique. For this purpose, high temperature oxidation tests were conducted in dry air for 96 h at 500, 600 and 700 °C to obtain the mass changed per unit of area at specific time intervals. Statistical techniques as described in ASTM G16 were used to formulate the oxidation mass change as a function of time. The cross-section and surface of the oxidized coatings were examined for both visual and chemical analyses using wavelength dispersive X-ray spectroscopy element mapping, X-ray diffraction and energy-dispersive X-ray spectroscopy. The results showed sub-parabolic oxidation behavior up to 600 °C and quasi-liner at temperatures between 600 and 700 °C for the coatings. The spectroscopy results showed formation of two Ni–Ti–O compounds (Ni₃TiO₅ and NiTiO₃) between the dispersed TiO₂ and nickel that can ultimately reduce the oxidation rate for the coatings.