An investigation on hot corrosion and oxidation behavior of cobalt-based superalloy L605 in the simulated aero-engine environment at various temperatures

Abstract

L605 is cobalt-based superalloy which has many potential applications in power generation sectors like gas turbines and boilers due to their elevated temperature strength and oxidation resistance. Changing corrosion resistance of this alloy, at elevated temperatures, is a cause of concern for its practical applications. In this paper, both hot corrosion and oxidation behaviour of this alloy was investigated in a salt environment of 87.5% Na2SO4 + 7.5% NaVO3 + 5% NaCl and air respectively. Three different temperatures of 650 °C, 750 °C and 850 °C were considered, for this analysis. The experiment consisted of 50 cycles where each cycles entails, 1 hr heating in a tubular furnace and 20 min of air cooling. Weight measurements of each sample were carried after each cycle. Thermogravimetric analysis showed that the corrosion rate is high in salt environment samples in comparison with that of air oxidized samples. The surface analysis of the samples was done using optical microscopy, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction analysis (XRD). As the temperature increases, more spallation was observed in hot corroded sample compared to that of oxidized sample, thus confirming high corrosion rate of hot corroded sample.