Effect of pre-oxidation on the moderate-temperature hot corrosion behavior of CoNiCrAlY-YSZ thermal barrier coatings

The hot corrosion behavior of the normal and pre-oxidation thermal barrier coatings in two corrosive media (Na2SO4 + NaVO3 and Na2SO4 + NaVO3 + NaCl) was conducted in this article. Before the hot corrosion experiment, the optimal pre-oxidation conditions were selected to form a continuous single thin layer of alpha-Al2O3 on the coating surface. The results showed that the coatings exhibit different failure behaviors in two corrosive media, and the mechanism of hot corrosion was explained. Notably, a coupling effect was observed among Na2SO4, NaVO3, and NaCl. Na2SO4 drove the basic corrosion attack on the ceramic top coat, thermally grown oxide (TGO), and the bond coat. Meanwhile, NaVO3 primarily strengthened the attack of Na2SO4 on the ceramic top coat, while NaCl enhanced the attack of Na2SO4 on TGO and bond coat. Furthermore, the pre-oxidation treatment effectively reduced the oxidation of the bond coat and the thickness of BDZ, and better extended the life of TBCs.