Outstanding durability of sol-gel thermal barrier coatings reinforced by YSZ-fibers

Abstract

Thermal barrier coatings (TBC) were fabricated with commercial powders of yttria stabilized zirconia with spherical and fiber-like morphologies. The influence of fiber percentage and sintering temperature on the thermomechanical behavior was studied. TBCs with 60%–80% fibers content had the best lifetime in cyclic oxidation with less than 10% of coating spallation after 1000 cycles, with very good reproducibility. They reached lifetimes higher than industrial TBCs made by EB-PVD. The enhancement of durability is believed to be due to an increase in the thermomechanical constraints accommodation thanks to higher porosity and higher tenacity due to the presence of well anchored fibers, indeed deviation of the cracks were observed. Moreover, the morphology of the thermally grown oxide (TGO) layer is also favorable as it includes anchorage points of the TGO with fibers. This increased the adherence at the substrate interface and improved lifetime.