Microstructure and Phase Evolution of Yb2sio5/Mosi2-Mullite Environmental Barrier Coatings at 1500 °C

Abstract

Water-vapor corrosion behavior of Yb2SiO5/MoSi2-Mullite double-layer environmental barrier coating on Nb based alloy at 1500 °C was investigated systematically. After initial oxidation, the thermal grown oxide (TGO) appearing undulating morphology under the dual action of growth stress and rigid displacement of coating were generated at the interface of Yb2SiO5 and MoSi2-Mullite layer, which induced serious tensile stress according to the theoretical simulation. Moreover, due to the internal diffusion of Yb2O3 and the water-vapor corrosion of Yb2SiO5, pores producing in the Yb2SiO5 layer induced continual thickening of TGO with an approximately line law, which derived horizontal cracking near the TGO layer.

Keywords: Microstructure and phase evolution, Yb2SiO5, MoSi2, Water-vapor corrosion, Nb alloy