The influence of thermal barrier coating dissolution on CMAS melt viscosities

Glassy deposits, largely consisting of CaO-MgO-Al2O3-SiO2 (CMAS), are a common product on thermal barrier coatings (TBCs) within gas-turbines after an interaction with airborne particles. Here, in order to facilitate the quantification and modelling of the spreading and infiltration behavior of CMAS melts onto and into TBCs we have determined the high temperature viscosities of four widely used synthetic CMAS melts and the influence of TBC materials (yttria-stabilized zirconia (YSZ) and gadolinium zirconate (GZO)) dissolution upon them. After a dissolution of 6.5 wt% YSZ or GZO one out of four CMAS melts shows no significant change in viscosity, while the other three melts exhibit a viscosity increase at lower temperatures that continuously changes to a decrease in viscosity towards higher temperatures. The influence of the doping amount on the viscosity was investigated in detail for one CMAS melt (C(35)M(10)A(7)S(48)) and parametrized.

Automated summary

This study determined the high temperature viscosities of four synthetic CMAS melts and their interactions with TBC materials. The results showed that after dissolving YSZ or GZO, most of the CMAS melts exhibited an increase in viscosity at lower temperatures followed by a decrease at higher temperatures.