Preparation of nanostructured Gd2Zr2O7-LaPO4 thermal barrier coatings and their calcium-magnesium-alumina-silicate (CMAS) resistance

Nanostructured 30 mol% LaPO4 doped Gd2Zr2O7 (Gd2Zr2O7-LaPO4) thermal barrier coatings (TBCs) were produced by air plasma spraying (APS). The coatings consist of Gd2Zr2O7 and LaPO4 phases, with desirable chemical composition and obvious nanozones embedded in the coating microstructure. Calcium-magnesium-alumina- silicate (CMAS) corrosion tests were carried out at 1250 °C for 1-8 h to study the corrosion resistance of the coatings. Results indicated that the nanostructured Gd2Zr2O7-LaPO4 TBCs reveals high resistance to penetration by the CMAS melt. During corrosion tests, an impervious crystalline reaction layer consisting of Gd-La-P apatite, anorthite, spinel and tetragonal ZrO2 phases forms on the coating surfaces. The layer is stable at high temperatures and has significant effect on preventing further infiltration of the molten CMAS into the coatings. Furthermore, the porous nanozones could gather the penetrated molten CMAS like as an absorbent, which benefits the CMAS resistance of the coatings.