Enhanced cyclic oxidation resistance through the self-healing of segmented cracks using nano-Al₂O₃/Ni-20 wt%Al particles in laser re-melted thermal barrier coatings

This paper introduces a novel and effective self-healing method of segmented cracks in laser re-melted ZrO₂-7 wt% Y₂O₃ thermal barrier coatings (TBCs). The method uses pressure sintering of nano-Al₂O₃/Ni-20 wt%Al particles at 1150 °C for 12 h. After treatment to facilitate self-healing, a very dense and metallurgically bonded nano-Al₂O₃ reinforced Ni-matrix sealed film formed in the segmented gaps. Cyclic oxidation results indicate that dense sealed films can effectively suppress the growth of thermally grown oxides (TGO) and prevent the formation of other brittle and fragile oxides (i.e., spinels) at the top coat/bond coat (TC/BC) interface. Using the pressure-sintering effect, any aluminums contained in the sealed particles or films becomes prone to diffusion into the TC/BC interface to facilitate the formation of a thin-continuous TGO during the initial oxidation. This results in a significantly enhanced anti-oxidation effect of laser re-melted TBCs.