Improvement of high-temperature oxidation resistance of titanium-based alloy by sol–gel method

Sol–gel dip coating of SiO₂ was applied on a TiAl-based alloy, and subsequent heat treatment was performed. XRD and SEM/EDS analysis revealed that an amorphous silica coating was formed on the alloy. Isothermal oxidation and cyclic oxidation at 600 and 700 °C in static air of the specimens with or without coating were performed to investigate the effect of the SiO₂ coating on the oxidation behavior of the alloy by thermogravimetry. The average parabolic rate constants of the coated specimens were greatly reduced due to the presence of the coating. Severe cracks and spallation of the scales were observed on the blank specimens, but not on the coated ones. The oxide scales formed on the uncoated specimens were stratified. For the coated samples, a mixture layer of rutile TiO₂ and Al₂O₃ occurred beneath the applied film.