Self-healing capacity of Mullite-Yb2SiO5 environmental barrier coating material with embedded Ti2AlC MAX phase particles.

Repetitive heating and cooling cycles inevitably cause crack damage of hot gas components of gas turbine engines, such as blades and vanes. In this study the self-healing capacity is investigated of mullite + ytterbium monosilicate (Yb 2 SiO 5) as EBC material with Ti 2 AlC MAX phase particles embedded as a crack-healing agent. The effect of Ti 2 AlC in the EBC was compared with the self-healing ability of the mullite + Yb 2 SiO 5 material. After introducing cracks by Vickers indentation on the surface of each sample, crack healing was realized by controlling the temperature and time during the post-heat-treatment process. For the mullite + Yb 2 SiO 5 composite with Ti 2 AlC particles, crack healing occurred at 1000 °C, while in the case of the mullite + Yb 2 SiO 5 composite without Ti 2 AlC, a sustained temperature of 1300 °C or higher was required. Compared with the healing of the mullite + Yb 2 SiO 5 composite by the formation of a eutectic phase, the addition of Ti 2 AlC promoted healing via the oxidation of Ti and Al. Notably, the surface formation of a ternary oxide of Ti–Yb–O was confirmed, which completely covered the damage area. Consequently, the addition of a Ti 2 AlC MAX phase to the EBC composite resulted in a complete strength recovery, while the mullite + Yb 2 SiO 5 composite without Ti 2 AlC showed a strength recovery of about 80%. Furthermore, by analyzing the indentation load–displacement curve to indicate the role of Ti 2 AlC, the addition of Ti 2 AlC improved both the hardness and stiffness of the composite. [ABSTRACT FROM AUTHOR]