The Effect of Hot Corrosion and Electrochemical Corrosion on Microhardness of the Coating

In this study, a NiCoCrAlY + lanthanum zirconate multilayer thermal barrier coating was deposited on Inconel 738 through the thermal plasma spray technique. The coated samples subjected to hot corrosion testing at 900 °C for 240 h after coating them with 90 wt.% Na2SO4 + 5 wt.% NaCl + 5 wt.% V2O5. The corroded samples were evaluated using SEM, SED, XRD, microhardness and electrochemical study. The dominance of vanadium was observed in the form of LaVO4 phase formation at the plates on the coating surface. The as-received coating sample, sample after the electrochemical test, sample after hot corrosion and hot-corroded sample after electrochemical test were tested for hardness. A significant decrease of 23.8% in hardness was measured after the electrochemical test of the corroded sample.