Oxidation of Columbium and coated Columbium Alloys
Abstract : microscopy, high temperatureniobium alloy su-31, niobium alloy fs-85, fluorescence, x raysOxidation of columbium alloys FS-85, SU-31, and a complex disilicide coating/SU-31 and FS-85 alloy systems has been studied in the temperature range 1400 to 2700 F at 1 atm and 50 Cm/sec flow rate of air. For studies of the uncoated alloys, the flow rate and pressure dependence of the alloys was also investigated. The experimental methods included thermogravimetric measurements of oxidation rates and studies on reacted specimens by means of X-ray diffraction, metallographic techniques, and electron microprobe analysis. Two anomalies in the temperature dependence of the oxidation. rate were observed for both alloys and were related to the oxides formed. The SU-31 alloy has the best oxidation resistance. The oxidation mechanism of the alloys is discussed along with the mechanism of protection afforded by the complex disilicide coating system. The coating did not fail after 1000 hours of oxidation