Self-healing TBCs: how micro-changes influence the overall coating durability

The concept of self-healing thermal barrier coatings (TBCs) centers on their ability to recover from microstructural damage caused by extreme thermomechanical loads and to autonomously restore functional properties to a near-initial state. In other words, the microstructural effects should enable macrostructural benefits, necessitating rather complex coating systems. This work presents the flexibility and adaptability of various plasma spray approaches for producing self-healing TBCs. Silicon carbide (SiC) was used as a healing agent and integrated into the state-of-the-art YSZ top coat. Different spray routines and various feedstocks were employed to carefully control the coating structure, limit the in-flight oxidation of SiC, and promote the so-called oxidation-driven self-healing capability. The microstructural evolution of the coatings under high-temperature conditions, specifically isothermal oxidation and thermal cyclic fatigue, was evaluated using high-resolution scanning electron microscopy (HR-SEM), energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) methods. The evolution of thermal transport properties resulting from the addition of SiC was also studied. This research facilitates a discussion on how the incorporation of carbide-based self-healing agents influences coating architecture and overall durability of TBC systems.