A comparative study on thermal shock resistance of plasma sprayed conventional layered structure, nanostructure and a new structure YSZ thermal barrier coatings

The microstructure, especially the pore structure, has a great influence on the sintering behavior and thermal shock resistance of the plasma sprayed thermal barrier coatings (TBCs). At present, conventional coatings with layered structure and nanostructured coatings with bimodal structure are the two most typical TBCs prepared by plasma spraying process. In this study, conventional layered structure, nanostructure and a kind of new composite structure YSZ TBCs that consists of dense coating matrix and embedded porous micron-aggregated particles were fabricated by air plasma spraying. The failure modes of three kinds of TBCs under burner rig thermal shock (BRTS) and furnace cyclic test (FCT) were investigated. In addition, the effect of microstructure on thermal shock resistance of different TBCs was analyzed. It was found that the degradation of strain tolerance of ceramic coat caused by sintering was the key factor leading to the cracking and failure of TBCs. Conventional TBCs suffered a premature spallation due to rapid sintering induced stiffening of the ceramic top coat. Since the newly-structured coating can maintain high strain tolerance during high temperature sintering, the lifetime of the new TBC was significantly longer than that of conventional and nanostructured TBCs under both BRST and FCT test.