|About this Abstract
||Materials Science & Technology 2011
||MS&T'11 Poster Session
||150 Analysis of Hf-Ta Alloys for Oxidation Protection in Ultra High Temperature Environments
||Otto Lu-Steffes, Elizabeth Colon, Ridwan Sakidja, John H Perepezko
|On-Site Speaker (Planned)
Materials with in-situ thermal protective coatings at high temperatures are of great interest for advanced aerospace applications. Hf-Ta alloys are being considered due to their attractive high-temperature materials properties. The oxide scale formation of Hf-Ta was studied at 1650°C through torch testing and 1200-1300°C through air furnace oxidation. The results show that the oxide scale is composed of HfO2 and between the interface of the scale and the alloy substrate there is a reaction zone that is composed of HfO2 and a Hf-Ta-O ternary oxide. The oxidation tests show that Ta additions to Hf significantly reduce the oxide thickness. The XRD results confirm that oxidized Hf-Ta alloys form monoclinic HfO2 and orthorhombic Hf7Ta2O19. Analysis of the results indicates that the beneficial effect of Ta is due to a reduced oxygen mobility in the ternary Hf-Ta oxides that form superstructures of the alpha PbO2 crystal prototype.