Thermal shock behaviors and mechanisms of ytterbium silicate environmental barrier coatings modified by MoSi2

Abstract

Rare-earth silicate environmental barrier coatings（EBCs）are important materials for the application in hot end components of new generation high thrust-to-weight ratio aero engines. However, the rare-earth silicate top layer is prone to form longitudinal cracks, which provides a channel for corrosive media to enter the interior of the EBC system, causing oxidation and cracking of the silicon bond layer, ultimately leads to the failure of EBCs under high temperature service environment. MoSi2 has excellent high-temperature properties and is expected to improve the high-temperature stability of rare-earth silicate EBC systems. In this work, three kinds of EBCs with Yb2SiO5, Yb2SiO5-5%MoSi2（Volume fraction，the same below）and Yb2SiO5-10%MoSi2 as the top layer, Yb2Si2O7 as the intermediate layer and Si as the binder layer were prepared by vacuum plasma spraying（VPS）technique respectively. The morphological changes of the coating before and after thermal shock at 1350 ℃ were characterized by field emission scanning electron microscopy. The doping of MoSi2 not only improves the damage tolerance of the Yb2SiO5 coating, but also consumes the oxidizing medium and reduces its diffusion into the interior of the coating system, which reduces the thickness of the TGO layer on the bonded layer by 83% and 88% and effectively improves the high-temperature stability of the coating system.

Keywords

• environmental barrier coatings
• ytterbium silicate
• mosi2
• thermal shock
• vacuum plasma spraying