Oxidation behavior of Fe-Cr-(Si)-Y

Abstract

Abstract Alloy engineering has become an increasingly important area of study that affords the designer with an increased number of available materials for use in unique environments and applications. One such alloy engineering opportunity is the development of oxide dispersed stainless steel processed via internal oxidation. Melt spun ribbons were used as a means to determine the mechanisms that govern oxide formation and the effect of sintering conditions on oxide growth in water atomized powder. The ribbon geometry was selected as a model system for water-atomized powder particles, to provide insight into oxidation reactions, rather than to precisely duplicate the conditions present during atomization. Experimental and theoretical analyses show that the yttrium-containing oxides are the most thermodynamically and kinetically stable oxide phases formed in the Fe-Cr alloy system studied. Silicon lowers the formation energy of the yttrium-containing oxides by binding the oxygen to form Y2SiO5 and Y2Si2O7 before it can react to form other oxides. Moreover, silicon increases the availability of oxygen during dissolution of SiO2. A theoretical model has been developed which shows that, with careful control of alloy composition and processing parameters, fine, thermally stable oxide phases can be formed evenly and in a controlled manner throughout the alloy.