Degradation behaviour and microstructural characterisation of HVOF-sprayed Cr₃C₂-NiCr cermet coatings in molten salt environment
by V.N. Shukla; R. Jayaganthan; V.K. Tewari
International Journal of Materials and Product Technology (IJMPT), Vol. 53, No. 1, 2016

Abstract: The present work investigated the cyclic high temperature degradation behaviour of high velocity oxy-fuel (HVOF) sprayed Cr₃C₂-NiCr coating deposited on 310S stainless steel (310S). The coated as well as uncoated specimens were exposed to molten salt (Na₂SO₄-60%V₂O₅) environment at 700°C under cyclic conditions. The kinetics of hot corrosion was established using thermogravimetric technique. The corrosion products were characterised using the techniques such as X-ray diffraction, FE-SEM/EDAX and X-ray mapping for elucidating the corrosion mechanisms. The Cr₃C₂-25%NiCr coating was found to be successful in maintaining its continuous contact with the alloy substrate during cyclic degradation under simulated laboratory condition. HVOF sprayed Cr₃C₂-25%NiCr coating on 310S alloy substrate is found to be very effective in reducing the corrosion rate in the aggressive environment at 700°C as observed from the present work. The oxide scales for Cr₃C₂-25%NiCr coated specimen were found to be intact and spallation-free. The parabolic rate constant of the coated specimen was lower than that of the bare specimen. The better hot corrosion resistance imparted by Cr₃C₂-NiCr coatings may be attributed to the formation of oxides of chromium, nickel and spinel of nickel and chromium.

Online publication date: Thu, 05-May-2016

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