A healing-constrained multi-objective design strategy for self-healing thermal barrier coatings: A modeling and simulation study

Conventional thickness design of thermal barrier coatings (TBCs) is mainly governed by thermal insulation and fracture-mechanics-based delamination resistance. As for self-healing thermal barrier coatings (SH-TBCs), such thermo-mechanical criteria alone are insufficient, because they do not determine whether a given architecture can provide adequate healing-agent supply to satisfy crack-sealing demand. In this study, a dimensionless healing sufficiency index, H , is introduced into the thickness design of an APS TiC-containing SH-TBC system to quantify the matching between healing-agent supply and crack-filling demand. On this basis, a healing-constrained multi-objective design strategy is established to balance thermal insulation, interfacial delamination resistance and self-healing functionality. The results show that, after considering the risks associated with insufficient healing and constrained crack-body expansion caused by excessive filling, approximately 80 % of the thickness designs previously regarded as feasible under conventional thermo-mechanical criteria are excluded. This indicates that thermo-mechanical criteria alone can substantially overestimate the true feasible design domain of SH-TBCs. A favorable thickness window is identified, corresponding to a TiC–Al 2 O 3 –YSZ (TAZ) layer thickness of 30–40 μm and a YSZ top-coat thickness of 160–200 μm. High-temperature oxidation experiments further show that the optimized thin-TAZ architecture retains effective crack-sealing capability and excellent thermo-mechanical match.