Hot Corrosion Behaviour of Thermal-Sprayed TiO2-Reinforced Cr2O3 Composite Coatings on T-22 Boiler Steel at Elevated Temperature

Abstract

In the present research work, hot corrosion behaviour of Cr2O3–wt%TiO2-reinforced coatings on ASME-SA213-T-22 boiler steel has been evaluated in the simulated boiler environment at a temperature of 800 ℃ under 50 cyclic thermal loading conditions. The TiO2 composition in Cr2O3 matrix was 10 and 20 wt%, and the coatings were developed by using high-velocity oxy-fuel thermal spray technique. Experiments were conducted under the molten salt environment of 40wt%Na2SO4–60wt%V2O5. The study was comparative due to variation in the composition of TiO2 content (10 and 20 wt%). The hot corrosion behaviour was studied by analysing weight change measurements, and corrosion products were analysed by SEM–EDS and XRD techniques. The Cr2O3–10wt%TiO2 and Cr2O3 20wt%TiO2 coatings were able to reduce the corrosion rate by 84.14% and 86.20%, respectively, in comparison to uncoated steel. The presence of TiO2 significantly decreased the corrosion rates. XRD peaks for Cr2O3–10wt%TiO2 and Cr2O3–20wt%TiO2 coatings showed TiO2 and Ti2O3 as major phases which are protective oxide layers. Increase in hot corrosion resistance was observed with increase in TiO2 content in Cr2O3 matrix.