Oxidation resistance of low-velocity oxy fuel-sprayed Al2O3-13TiO2 coating on nickel-based superalloys at 800 °C

Abstract

Oxidation of metals and alloys has been recognized as a serious problem for high-temperature applications such as boilers, internal combustion engines, gas turbines, fluidised bed combustion and industrial waste incinerators. Superalloys are used in these applications because of their excellent strength and creep resistance at high temperature, but these alloys lack resistance to oxidation. In the present investigation, Al2O3-13%TiO2 coating is deposited on nickel-based Superni 718 and AE 435 superalloys using a low-velocity oxy fuel (LVOF) process. The coating has been characterised for scanning electron microscopy (SEM), X-ray diffraction (XRD) and surface roughness. Cyclic oxidation experiments were conducted for 50cycles, with each cycle consisting of keeping the samples at 800°C for 60min followed by 20min of cooling in air. The weight change measurements were taken to establish the oxidation kinetics of the coated and uncoated superalloys. The LVOF sprayed Al2O3-13%TiO2 coating has shown good oxidation resistance as well as adherence to the substrates under the tested environment. The AE 435 superalloy has shown lower oxidation rates in comparison to Superni 718 superalloy.