Evaluation of hot corrosion performance of HVOF coatings on PCGTA welded Fe-based alloy A-286 in Na2SO4%-7.5%NaVO3%-5%NaCl environment

Abstract

This research article investigated the hot corrosion behaviour of the pulsed current gas tungsten arc (PCGTA) welded Fe-based alloy A-286. PCGTA welding is employed to obtain a similar joint of 6 mm plates of A-286 alloy using ER-320LR filler material. A high-velocity oxy-fuel (HVOF) coating is carried out to deposit Cr3C2-25%NiCr and Ni-20%Cr coating on the PCGTA weldments. The microstructure and elemental analysis of the surface and cross-sections of the coatings were examined by Scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS). Hot corrosion study is carried out on bare, and HVOF coated PCGTA weldments in Na2SO4-7.5%NaVO3-5%NaCl environment at 850 °C. The corrosion frate of the weldments was determined by thermogravimetric analysis. The reaction products present in the weldments were characterized by SEM and x-ray diffraction (XRD) analysis. Depths of corrosion attack and elemental distribution on the weldments at cross-section are analyzed using EDS with the x-ray mapping technique. The Cr3C2-25%NiCr coated weldment exhibits the superior corrosion resistance than bare and the Ni-20%Cr coating due to the development of chromium oxide (Cr2O3) scales. The chromium carbide coating has a reduced weight gain of 56% and 25% compared to uncoated, and Ni-20%Cr coated specimens.