Multilayered Thermal Barrier Coating for Land-Based Gas Turbines

Abstract

Multilayered thermal barrier coatings (TBC) with different functions were proposed for the hot section components of land-based gas turbines. This article describes a multilayered TBC with an oxidation resistant layer. A conventional duplex TBC and a triplex TBC, in which an aluminized layer was added to the conventional duplex TBC to increase oxidation resistance, were prepared. It was confirmed by a burner rig test that the triplex TBC with the aluminized layer is resistant to oxidation and shows high durability in a thermal cycle test, compared with the conventional duplex TBC. The spalling in the thermal cycle test of each TBC specimen occurred at the same position, when the thickness of the oxidation layer was 11 to 13 µm. The mechanism of spalling of the coating in the thermal cycle test was discussed in terms of stress in the coating. Stress in the direction of spalling occurred by an uneven interface between the bond and top coat and increased with growth of the oxidation layer. It is thought that the high durability of the triplex TBC in the thermal cycle test is derived from suppressing the growth of the oxidation layer and decreasing the stress due to the addition of the aluminized layer.