Comparative hot corrosion performance of APS and Detonation sprayed CoCrAlY, NiCoCrAlY and NiCr coatings on T91 boiler steel

• Published in: Corrosion science Vol. 189; p. 109556
• Main Authors: C., Sundaresan, B., Rajasekaran, S., Varalakshmi, K., Santhy, Rao, D. Srinivasa, G., Sivakumar
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 15.08.2021; Elsevier BV
• Subjects: A. Cobalt; A. Metal coatings; A. Nickel; Aluminum oxide; B. SEM; B. XRD; C. Hot corrosion; Chromium oxides; Corrosion resistance; Corrosion resistant steels; Detonation; Heat resistant steels; Hot corrosion; Martensitic stainless steels; Potassium sulfate; Protective coatings; Salt deposits; A. Nickel; B. SEM; B. XRD; A. Metal coatings; A. Cobalt; C. Hot corrosion
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2021.109556

•DSC coatings offered better hot corrosion resistance than the APS coatings.•NiCr composition provides excellent corrosion resistance under molten salt enviorment.•Chromia and spinel oxides resisted hot corrosion ingress in coatings.•Lack of SO2 caused lower stability of Alkali iron trisulphates and primarily oxidation attack.•DFT analysis performed to validate the thermodynamic stability of oxides formed. Hot corrosion performance of Atmospheric Plasma Spray (APS) and Detonation spray (DSC) CoCrAlY, NiCoCrAlY, and NiCr coatings on T91 steel were investigated at 650 °C for 100 cycles under Na2SO4-K2SO4-Fe2O3 mixed salt deposit in ambient air. The hot corrosion resistance of DSC coatings was found to be superior to their APS counterparts. Chromia and spinel oxides provided excellent corrosion resistance while no α-Al2O3 was observed. DSC NiCr and APS NiCoCrAlY offered the most and the least corrosion resistance, respectively. DFT calculation was performed to validate the thermodynamic stability of each oxide and identify the precise oxide formation.