Mitigation of damage from molten fly ash to air-plasma-sprayed thermal barrier coatings

► High-temperature effects of fly-ash deposits on ceramic TBCs for syngas-fired gas-turbine engines are examined. ► Molten fly ash penetrates the entire thickness of conventional 7YSZ TBCs destroying them. ► Alternative TBCs of Gd2Zr2O7 composition are highly resistant to this type of damage. ► Arrest of fly-ash penetration in Gd2Zr2O7 TBCs is due to the formation of an impervious reaction layer at the interface between the TBC and the fly-ash layer.