The Effect of Bond Coat Roughness on the CMAS Hot Corrosion Resistance of EB-PVD Thermal Barrier Coatings

Abstract

In a high-temperature, high-flame-velocity, and high-pressure gas corrosion environment, the intercolumnar pores and gaps of electron beam–physical vapor deposition (EB-PVD) thermal barrier coatings (TBCs) may serve as infiltration channels for molten calcium–magnesium–alumino–silicate (CMAS), leading to the severe degradation of TBCs. In order to clarify the relationship between the roughness of the bond coat and the CMAS corrosion resistance of the EB-PVD TBCs, 7 wt.% yttria-stabilized zirconia (7YSZ) TBCs were prepared on the surfaces of four different roughness-treated bond coats. The effect of the bond coat roughness on the columnar microstructure of the EB-PVD YSZ was investigated. The effect of the change of the bond coat’s microstructure on the CMAS corrosion resistance of the EB-PVD YSZ was studied in detail. The results showed that the reduction in the roughness of the bond coat contributes to the improved formation of the EB-PVD YSZ columns. The small and dense columns are similar to a lotus leaf-like structure, which could reduce the wettability of CMAS and minimize the spread area between the coating and the CMAS melt. Thus, the CMAS corrosion resistance of the coating can be greatly improved. This preparation process also provides a reference for the preparation of other TBC materials, improving the resistance to CMAS hot corrosion.

A Comprehensive Understanding of Thermal Barrier Coatings (TBCs): Applications, Materials, Coating Design and Failure Mechanisms

“…Another important aspect is the roughness of the BC, which significantly influences the lifespan of the TBCs. Proper roughness aids in the adhesion of the TC with a uniform distribution of mechanical stresses, while excessive roughness can lead to stress concentrators that may cause cracking and delamination [84,85].…”

Hot-Corrosion Behavior of Gd2O3–Yb2O3 Co-Doped YSZ Thermal Barrier Coatings in the Presence of V2O5 Molten Salt

“…The ceramic topcoat typically contains 7-8 wt% Y 2 O 3 -stabilized ZrO 2 (YSZ), which possesses several desirable characteristics for TBC applications, including a high melting point, low thermal conductivity, thermal expansion coefficient similar to that of the substrate, and high toughness [1,6]. The most commonly used TBC fabrication technologies are air plasma spraying (APS), electron-beam physical vapor deposition, and plasma-spray physical vapor deposition [7][8][9][10][11][12]. The YSZ TBCs fabricated in their original state exhibit a desirable metastable tetragonal prime phase (t ), owing to their high toughness and suitability for TBC applications.…”