Hot Corrosion Study of Ni-Cr Alloys

摘要

The hot corrosion behavior of three nickel basealloys are investigated in fused salts (Na2SO4 - 10 wt% NaCl)environment. The oxidation kinetics, scale morphologies,phases and porosity are measured by thermo gravimetricanalysis (TGA), Field electron microscopy (FE-SEM), EDSand image analyzer respectively. In addition to FE-SEManalysis, microstructure of the samples are seen by opticalmicroscope. Susceptibility to hot corrosion was found to becorrelated to the scale formed during oxidation. Alloyscontaining Cr as an element, they formed Cr2O3 scale onsurface which is stable, below 800oC, but above 800oC, Crform CrO3 scale which is volatile in nature. In case of alloywith Al as an inhibitor forms stable alumina scale above8000C, which reacts with fused salt and formed NaAlO2(Sodium aluminate) which has high melting point (1650oC),thus, it is stable at high temperature. The relevant hotcorrosion mechanisms are discussed.