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.