Preparation and high temperature oxidation behaviors of TiO2/Al2O3/Inconel625 composite coatings on the surface of Q235 alloy at 900 °C

Abstract

Sol-gel method combined with plasma surfacing was used to prepare TiO2/Al2O3/Incone1625 composite coatings on the surface of Q235 alloys. Oxidation thermodynamic results show the composite coatings caused lower oxidation weight gain than the sample with single coating. Combination of XRD and SEM results illustrates that the surface and cross-sectional morphology were composed of an innermost continuous but not compact enough Cr2O3 layer, the outer layer next to C2O3 was loose and cracked NiO, and the outermost layer was composed of iron oxides for the Incone1625 coated sample. For the composite coating sample, the oxide film was composed of NiO as the outermost layer, Cr2O3 as the inner layer, there was a very thin but continuous layer consisted of Cr2O3 and Al2O3 as the innermost layer. This work shows that TiO2/Al2O3/Incone1625 composite coating improves the high-temperature oxidation resistance properties of the Q235 alloy at 900 °C by promoting the formation of the protective Cr2O3 and Al2O3 film.