Development of MoSi2-based sacrificial particles for self-healing thermal barrier coatings

Thermal barrier coatings (TBCs) are applied on the surface of metallic components of
modern jet engines such as combustion chambers, blades and vanes, in order to increase the
engine efficiency by allowing higher operating temperatures. However, during cooling from
the operating temperature (i.e. 1000 °C) to room temperature high stresses develop in the
ceramic coating due to mismatch of the coefficient of thermal expansion between the metal
substrate and ceramic TBC. Then, micro-cracks are generated which, ultimately, lead to the
failure of the TBC system. Yttria partially stabilized zirconia (YSZ) is the state-of-art
material in industrial TBCs. Since YSZ does not exhibit any self-repair, it is highly desirable
to develop new TBC materials with a prolonged lifetime. This can be achieved by addition
of MoSi2 intermetallic particles to the YSZ base material. Upon exposure to high-temperature
and an oxidizing environment via the crack-path, these MoSi2 particles decompose into a
volumetrically expanding product which fills and seals the crack...