LaNdZrO thermal barrier coatings by electron beam physical vapor deposition: Morphology, thermal property and failure mechanism

Abstract

Thermal barrier coatings (TBCs) have been widely studied over the last decade. Lanthanum zirconate (LaZrO) is known for high melting point and good thermal stability in aircraft engine environment. The thermal property and failure mechanism of these advanced TBCs still remain a challenge. This study focuses on phase structure, thermal expansion coefficient, thermal conductivity, morphology, composition, thermal durability, and failure behaviors in the LaNdZrO/YSZ/NiCoCrAlYHf TBCs. The LaNdZrO and YSZ ceramic coatings have been deposited by EB-PVD, and NiCoCrAlYHf metallic coating has been deposited by AIP-PVD. The as-deposited TBCs exhibit good thermal cycling life and thermal shock life at 1100 °C due to the improvement of TEC and the formation of feathery microstructure. In the thermal durability test, the locally broken region of the YSZ/TGO interface, YSZ coating and further the LaNdZrO coating might facilitate propagation of the instability. The element diffusion and cracks evolution might be two critical factors for the failure mechanism of TBCs. This study would further explain the failure of other advanced TBCs.