Hot corrosion behaviour of Inconel 738 superalloy in presence of NaCl, Na2SO4, V2O5

Abstract

Superalloy are widely used for high temperature applications in diverse environment such as boilers, turbines and petrochemical industries for longer hours of operation. The application environment may have aggressive salts such as NaCl, Na2SO4, V2O5 which can catalase the hot corrosion thus affecting the normal working of the appliances. In present work, hot corrosion behavior of Inconel 738 superalloy studied by using cyclic hot corrosion test carried out at 700 °C for 10 cycles. For this study to know how the effect of salts on the alloy, each specimen was coated separately by NaCl, Na2SO4, V2O5 salt. After that, the coated specimens placed in the furnace. The cycle consists of 24Hr of heating at 700 °C in muffle furnace. Then, the specimens removed from the furnace and allowed to cool in the air environment. The weight gain after every cycle is measured and is used to determine the kinetics of hot corrosion. The graph of square of weight gain/Area Vs no of cycles was plotted. X-ray diffraction used to study the different types of oxides and compounds formed on the specimen surface. The morphology and electrochemical analysis of the specimens correlated to study the hot corrosion behavior. The rate constant (parabolic rate constant, KP) was determined from the weight gain data. The results showed that the specimen coated with Na2SO4 has lower corrosion as compare to the specimen coated with NaCl and V2O5 due to the presence of protective oxide such as Cr2O3, TiO2, Fe2O3, NiCr2O4, Ni3Ti formed on the specimen surface.