HEALING PARTICLES IN SELF-HEALING THERMAL BARRIER COATINGS

Crack healing in ceramic thermal barrier coatings (TBCs) may be realized by embedding Mo-Si based particles in the thermal barrier coating. Upon cracking, these particles are exposed to oxygen that permeates through the top layer and the crack gap is filled with SiO2 which is produced from oxidation at high temperature. Due to its amorphous characteristics and expanding oxide volume, SiO2 is able to fill a significant portion of the crack. Simultaneously, Mo forms a volatile oxide (MoO3) that may leave the coating through the crack path and subsequently through pores, thereby compensating for the volume increase upon oxidation. The present work combines an experimental and modelling approach to develop and characterize the healing particles in the TBC system. In particular, two issues have been addressed, namely (i) the manufacturing of the healing particles that are to be embedded in the coating and (ii) the characterization of damage in TBC systems in order to identify the optimal properties of the healing particles.