Hot corrosion performance of bare and coated T91 steel under actual and simulated bio-fuel fired boiler environment

Abstract

The conventional fuel has now been replaced by bio-fuels, due to an increasing demand of power supply which has only been met through the non-renewable resources so far. However, burning of bio-fuel creates corrosive atmosphere which is different from that of coal and oil firing. Therefore, in the present investigation, bare and coated boiler steel T91 substrates were exposed to real andsimulated bio-fuel fired boiler environment working at high temperature. It was noticed that dense and protective oxide was present on Cr3C2-NiCr coated T91 steel after 50hours of exposure in the simulated environment which depicts the protective behaviour of the coating and compatibility of coating with steel despite of variation in the composition. However, oxide so formed in actual bio-fuel fired boiler was porous. WC-Co coated T91 steel has undergone severe corrosion by showing the oxide spallation and delamination of the coating from the substrate under a simulated environment. Similar observations were noticed in the actual boiler working at the temperature of 750±50°C.