Sc-doped Gd2Zr2O7 coating on YSZ thermal barrier coatings to resist CMAS plus molten salt attack

Coupling corrosion resulting from calcium-magnesium-alumina-silicate (CMAS) and molten salt causes severe attack to YSZ thermal barrier coatings (TBCs). In this study, a Sc-doped Gd2Zr2O7 (GZO-Sc) coating is prepared on the YSZ coating to alleviate CMAS + NaVO3 (CN) corrosion. Results revealed that the GZO-Sc coating largely prevented CN (with a melting point of 1188 ?) attack to YSZ coatings at 1200 ? and 1250 ?. At the test temperatures, CN melted and penetrated the GZO-Sc coating, during which the melt and the coating reacted to form a dense reaction layer, consisting of Gd8Ca2Si6O26-based apatite and c-ZrO2 based fluorite phase independent on the temperature and time. With the increase of the dwell time, V was separated from CN melt during infiltration, causing many CaAl2Si2O8 crystals at the bottom of the reaction layer and a V-rich layer beneath the reaction layer, which were beneficial to the CN corrosion resistance of the coatings.

Automated summary

In this study, a Sc-doped Gd2Zr2O7 coating is prepared to alleviate the coupling corrosion caused by CMAS and molten salt. The results show that the GZO-Sc coating effectively prevents the attack of CN on YSZ coatings at high temperatures. The reaction between CN and the coating forms a dense reaction layer, and the presence of CaAl2Si2O8 crystals and V-rich layer in the coating improves its corrosion resistance to CN.