Enhanced adhesion resistance of an 8YSZ thermal barrier coating trough the formation of zircon and mullite as self-healing reaction products under cyclic oxidation conditions

Abstract The formation of ZrSiO4 (zircon), 3Al2O3·2SiO2 (mullite), and amorphous SiO2 as healing products from the oxidation reaction of the SiC (silicon carbide) self-healing agent, occurred after 250 h of thermal exposition (ten thermal cycles of 25 h at 1100 °C). By SEM and TEM analysis of adhesion fracture surfaces, both zircon and mullite complex oxides were identified mainly along micro-cracks adjacent to theTGO-TC interface and forming bridges-like bonds with the ZrO2-TC and Al2O3-TGO compounds. Then adherence resistance seems to be enhanced by the formation of these bonds and by the mere presence of self-healing products retarding or blocking crack propagation.