An investigation of corrosion resistance of HVOF coated ASME SA213 T91 boiler steel in an actual boiler environment

Abstract

Purpose This paper aims to use the high-velocity oxy fuel (HVOF) spraying process for depositing 93(WC–Cr 3 C 2 )–7Ni, 75Cr 3 C 2 –25NiCr, 83WC–17C O and 86WC–10C O –4Cr coatings on ASME SA213 T91 to study the corrosion resistance of these coatings in an actual boiler environment. Design/methodology/approach The HVOF spraying process was used for depositing 93(WC–Cr 3 C 2 )–7Ni, 75Cr 3 C 2 –25NiCr, 83WC–17C O and 86WC–10C O –4Cr coatings on ASME SA213 T91. All the coatings obtained are found to be uniform, dense and having thickness between 200 and 250 μm. All the coatings were exposed in an actual boiler environment at 900°C temperature for 10 cycles. Each cycle consisted of 100 h heating followed by 1 h cooling at ambient conditions. X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy techniques were used to analyse corrosion products. Findings All the coated samples were found to be having higher corrosion resistance than the uncoated samples. Among coated specimens, 93(WC–Cr 3 C 2 )–7Ni coating has shown maximum and 75Cr 3 C 2 –25NiCr coating has shown minimum resistance to corrosion. Originality/value This paper is original research.