Zirconium Modified Aluminide by a Vapour Pack Cementation Process for Thermal Barrier Applications: Formation Mechanisms and Properties

摘要

The main mechanism of degradation of thermal barrier systems is the spallation of the thermally grown oxide (TGO) formed at the ceramic/metallic sub-layer. Present trends are the use of a platinum modified nickel aluminide layer as metallic sub-layer. But the effect of few p.p.m. or few % at. of zirconium on the oxidation of hipped or cast nickel aluminide was also studied for higher temperature applications. It has been shown that the system ZrO_2-Y_2O_3 (8% mass.) EBPVD / cast NiAl(Zr) had at 1200℃ a life durability three times longer than the classical system ZrO_2-Y_2O_3 (8% mass.) EBPVD/NiAlPt coatingickel base superalloy. Similar encouraging results were obtained with the system ZrO_2-Y_2O_3 (8% mass.) EBPVD / NiAl(Zr) coating deposited by physical vapour deposition/ nickel base superalloy. In this work, a zirconium modified nickel aluminide coating by vapour pack cementation process was developed. The structure of this modified coating is discussed. Cyclic oxidation test results and microscopic investigations are also presented.