Effects of Yttrium on the Oxidation Behavior of Low Sulfur Content Fe-Cr-Al Alloys for Heat Resistant Wires

The melting of FeCrAl-Y alloy in an electric furnace allows for a very low sulfur content to be obtained, of around 5 ppm or less. So, the question of the necessary quantity of yttrium to add in this ferritic alloy to reach the application requirements is once again of interest. Laboratory heats of FeCrAl with yttrium additions from 0 to 1,510 ppm and a parts per thousand currency sign6 ppm of sulfur content were melted, processed and studied. Oxidation kinetics in dry air were measured, using thermogravimetric measurements. High resolution scanning electron micrographic examinations provided a good description of the alumina oxide scales. These investigations were completed with a quantification of secondary phases according to the yttrium content of each melt. The results were analyzed using the oxidation mechanisms in relation to the yttrium content. Finally, a moderate level of yttrium was defined to reach the longest lifetime during the cyclic oxidation test of the commercial Resistohm(A (R)) Y grade.