Comparative Evaluation of Oxidation Resistance of Detonation Gun-Sprayed Al2O3–40%TiO2 Coating on Nickel-Based Superalloys at 800 °C and 900 °C

Abstract

High-temperature oxidation is the major degradation mechanism of boiler and gas turbine components. Superalloys are used in these applications because of their superior mechanical properties and creep resistance, but they lack resistance to oxidation under aggressive environment. In the present investigation, Al2O3–40%TiO2 coating was deposited on Superni718 and Superni600 superalloys by a detonation gun spray process. The as-sprayed coating was characterized by SEM analysis. The high-temperature oxidation behavior of Superni718 and Superni600 and Al2O3–40%TiO2 coating on these superalloys was evaluated in air under cyclic conditions at 800 °C and 900 °C for a total duration of 50 cycles. Each cycle consisted of keeping the samples for one hour at the elevated temperature followed by 20 min cooling in ambient air. Oxidation kinetics were studied using a thermo-gravimetric technique and found to follow the parabolic rate law. The coating was successfully formulated using a detonation gun spray process. The coating was found to be adherent to the substrate superalloys. It was found that among the two alloys, uncoated and coated Superni600 superalloys have much better oxidation resistance as compared to uncoated Superni718 superalloy.