Adhesion energy of a YPSZ EB-PVD layer in two thermal barrier coating systems

In order to understand the degradation of thermal barrier coating (TBC) systems better, we determined the adhesion energy (Gc) between the bond coat and the top coat and its evolution during cyclic oxidation. This energy was evaluated by means of a modified four-point bending test. The systems tested consist of a YPSZ (7 wt.%Y2O3–ZrO2) EB-PVD ceramic top coat deposited on a single-crystal AM1 superalloy substrate protected with either a β-(Ni, Pt)Al bond coat or a newly developed Zr-doped β-NiAl bond coat. Although the results show a similar adhesion evolution for both systems, different microstructural degradations are involved.