Enhancing the performances of EB-PVD TBCs via overlayer Al-modification

Abstract

Thermal barrier coatings (TBCs) guarantee the service life of high-temperature alloy substrates under harsh service environments. Premature failure of TBCs due to coating fracture, high-temperature oxidation, and calcium oxide–magnesium oxide–aluminum oxide–silicon oxide (CMAS) corrosion, which significantly reduce their service lifespan. In this study, Al film was applied on the surface of EB-PVD TBCs using arc ion plating, and then converted it to α-Al2O3 by an in situ reaction between Al and ZrO2. The α-Al2O3 have toughening effect resulting in a higher bending resistance of EB-PVD TBCs. Because α-Al2O3 could seal the columnar inter-crystal gaps on the surface of EB-PVD TBCs, it reduced oxygen penetration, which enhanced the high-temperature oxidation resistance. CMAS reacted with α-Al2O3 to generate spinel and calcium‑aluminum yellow feldspar compounds at 1350 °C, which prevented following CMAS penetration and corrosion. Furthermore, Al-modification reduced the surface roughness, which made Al-modified TBCs have better wetting resistance.