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

Abstract

This paper introduces a novel and effective self-healing method of segmented cracks in laser re-melted ZrO2-7wt% Y2O3 thermal barrier coatings (TBCs). The method uses pressure sintering of nano-Al2O3/Ni-20wt%Al particles at 1150°C for 12h. 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.