Effect of pre-aluminization on the properties of ZrO2-8wt.% Y2O3/Co-29Cr-6Al-1Y thermal-barrier coatings

Specimens of investment-cast Mar-M247 superalloy were vacuum-plasma sprayed with Co-29Cr-6Al-1Y bond coat, and part of the specimens were further pre-aluminized at 980°C for 2, 4, 6, 8, and 10 hours. All the specimens were then deposited with ZrO2-8 wt.% Y2O3 thermal-barrier coatings (TBCs) and thermally cycled at 1050°C to evaluate the effect of time of the prealuminizing treatment on the performance and failure mechanism of the modified system. Results showed that TBC specimens with pre-aluminized bond coatings exhibited lower oxidation rates and significantly higher cyclic life when compared with unaluminized specimens. The failure of bond-coat pre-aluminized TBC specimens was observed to propagate mainly along the lamellar splats of the top coat, whereas the failure of conventional TBC specimens occurred mainly along the top-coat/spinel oxides interface.