Hot Corrosion Behaviour of CNT Reinforced Zirconium Yttrium Coatings in Molten Salt Environment

Abstract

The present work investigates the hot corrosion behaviour of CNT-reinforced zirconium yttrium coatings on T-91 boiler tube steel in a molten salt (Na2SO4–60 wt%V2O5) environment at 600 °C under cyclic conditions. Air plasma spray technique was used for the development of coatings. The un-coated coated and all the as-coated specimens were subjected to hot corrosion exposure in a silicon tube furnace at 600 °C for 50 cycles. The corrosion behaviour was examined through mass gain measurements after the completion of each cycle. The corroded product was examined by XRD and SEM with EDAX analysis. After critical examination it was concluded that the oxide scale of Fe2O3 was formed on un-coated specimen as a result of it suffered from thermal spallation. All the as-coated specimens show the lower mass gains with good adhesiveness of oxide scale with the substrate steel. The CNT-reinforced zirconium yttrium coatings was found to provide better corrosion resistance in the hot corrosion environment due to uniform dispersion of CNT in the coatings matrix and the formation of protective zirconium oxide in the scale.