Hot corrosion behavior of plasma sprayed FeCrNiC and FeCrNiC/Cenosphere coatings on ASTM-SA213-T22 steel

Abstract

The steel alloys tubes used to manufacture boilers which are used in high temperature environment in thermal power plants are often subjected to high temperature corrosion. Therefore, to protect the surface of boiler tubes, protective coatings are used to counter the corrosion. In this work FeCrNiC and FeCrNiC/Cenosphere coatings deposited on T22 boiler tube steel using atmospheric plasma spraying. Thermocyclic hot corrosion studies were examined in a liquid salt condition of Na<inf>2</inf>SO<inf>4</inf>-60%V<inf>2</inf>O<inf>5</inf> for 17 cycles of 51 h at 600 °C on uncoated and coated steel. Thermogravimetric practice was utilized to build up the kinetics of hot corrosion of uncoated and coated steel. As-coated samples are studied for microstructure and microhardness. The X-ray diffraction(XRD), Scanning electron microscopy(SEM)/Energy dispersive spectroscopy(EDX), and X-ray mapping characterization techniques were used to analyse the corrosion products. It was observed that FeCrNiC/Cenosphere coated steel showed better hot corrosion resistance than the uncoated steels. Parabolic rate constant values of coated steel are lower in comparison to the uncoated steels. Better resistance is provided by high-temperature stability of mullite, alumina, defensive glassy oxide layer of silicon, titanium and spinels of chromium and carbon that is formed at elevated temperatures. © 2021