Elevated temperature oxidation behavior of HVOF sprayed TiB2 cermet coating

Oxidation behaviors of Ni(Cr)-TiB2 coating deposited by HVOF technique were studied at 800, 900 and 1 000°C in air. The microstructures of as-sprayed and oxidized coatings were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). After oxidation at 800°C, a thin and adherent oxide layer was formed on the surface of the coating. With increasing exposure temperature, the thickness of the oxide layer increased; and at 1 000°C the oxide layer separated from the coating. Investigation of the kinetics of oxidation by using the thermogravimetric analysis (TGA) technique shows a parabolic oxidation rate.