Degradation of EB-PVD ZrO₂-4 mol%Y₂O₃ thermal barrier coatings by volcanic ash deposits

This work describes the degradation of ZrO₂-4 mol%Y₂O₃ (YSZ) coatings obtained by EB-PVD. YSZ coatings were exposed at 1200°C for 10 min-50 hr by isothermal heat treatment in the presence of an erosive impurity of volcanic ash. At the interface between the YSZ coatings and volcanic ash, the coatings were partially dissolved in the volcanic ash, resulting in the degradation of coatings by the formation of the reacted region. A ZrSiO₄ or glassy phase is formed by the chemical reaction between YSZ coatings and volcanic ash at 1200°C. The chemically reacted region from the top surface of the YSZ coatings showed a tendency for increased degradation depth with an increase in isothermal heat-treatment time.