High-temperature interface stability of tri-layer thermal environmental barrier coatings

Thermal environmental barrier coatings (TEBCs) are capable of protecting ceramic matrix composites (CMCs) from hot gas and steam. In this paper, a tri-layer TEBC consisting of 16 mol% YO1.5 stabilized HfO2 (YSH16) as thermal barrier coating, ytterbium monosilicate (YbMS) as environmental barrier coating, and silicon as the bond coating was designed. Microstructure evolution, interface stability, and oxidation behavior of the tri-layer TEBC at 1300 & DEG;C were studied. The as-sprayed YSH16 coating was mainly comprised of cubic phase and-3.4 vol% of monoclinic (M) phase. After 100 h of heat exposure, the volume fraction of the M phase increased to-27%. The YSH16/YbMS interface was proved to be very stable because only slight diffusion of Yb to YSH16 was observed even after thermal exposure at 1300 & DEG;C for 100 h. At the YbMS/Si interface, a reaction zone including a Yb2Si2O7 layer and a SiO2 layer was generated. The SiO2 & nbsp;grew at a rate of-0.039 mu m2/h in the first 10 h and a reduced rate of 0.014 mu m(2)/h in the subsequent exposure.