Sintering and Phase Transformation Behavior of High-Purity Nanocrystallized Thermal Barrier Coatings at Very High Temperatures

High-purity nanocrystallized YSZ powders were used to manufacture thermal barrier coatings by air plasma spraying. After spraying, the coating samples were aged at temperatures of 1200, 1300, and 1400 °C. Coating samples made from ordinary YSZ powders were aged at the same temperatures. XRD analysis shows significant tetragonal-to-monoclinic phase transformation in the reference coatings after 100 h at 1400 °C in contrast to the phase stability exhibited by high-purity YSZ. The sintering behavior of the YSZ coatings was also examined along with the influence of MCrAlY oxidation.