Microstructure and self-healing properties of multi-layered NiCoCrAlY/TAZ/YSZ thermal barrier coatings fabricated by atmospheric plasma spraying

In this paper, the multi-layered self-healing thermal barrier coatings (TBCs) have been fabricated by atmospheric plasma spraying (APS). The phase composition of the sprayed feedstock and the as-sprayed coating have been characterized. The thickness of each layer for the self-healing TBCs have been optimized based on previous finite element simulation results. The self-healing effect of the TBCs under burner rig test (BRT) has been characterized via in-situ acoustic emission technique. The self-healing ability of the TBCs has been also characterized via static high temperature oxidation test. The investigation results indicate that the thickness of each layer for the as-sprayed self-healing TBCs is nearly in our optimization range based on our previous work. The AE signals of the TBCs before and after self-healing are distinctly different. When the self-healing effect has appeared, some key AE signals for the crack propagation has disappeared. The AE signals which are located at the higher frequency have been inhibited at a certain degree. The static high temperature oxidation results indicate that the TBCs with self-healing effect has lower oxidation rate compared with that of the TBCs without self-healing. The effective thickness of the TGO layer for the TBCs with self-healing treatment is lower compared with that of the TBCs without self-healing treatment.