A review of the technologies to achieve self-healing in YSZ thermal barrier coatings

Thermal barrier coatings (TBCs), advanced ceramic systems, are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, the layers of the TBC system expand and contract unevenly due to the mismatch in the coefficients of thermal expansion of the TBC layers. The resulting thermal stresses cause the nucleation and growth of microcracks in the TBC system. After a few hundred thermal cycles, the microcracks eventually combine and form a relatively large crack that causes spallation and separation of coating, exposing parts to high temperature and ultimately leading to catastrophic failure of the entire equipment. The creation of self-healing capability provides the ability to repair cracks spontaneously. In this article, various technologies for achieving self-healing in YSZ thermal barrier coatings and the structure and properties of the resulting coatings have been introduced and reviewed. After extracting the technologies of applying self-healing thermal barrier coating and comparing them with each other, it is possible to obtain coatings with self-healing properties according to the needs of each industry and then determined the proper composition of the self-healing coating, the proper thickness of the self-healing coating layer, the proper arrangement of the self-healing coating layer and the parameters of the coating process.