J. Phys. IV France 120 (2004) 47-54
Oxide reduction and diffusion in Fe-Cr alloy honeycombsJ.H. Nadler1, T.H. Sanders Jr.1, J.K. Cochran1 and S.S. Kim2
1 Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, Georgia, 30332-0245, USA
2 Hong Ik University, School of Materials Science and Engineering, Jochiwon 339-701, Korea
The goal of this study is to develop practices for evaluating and predicting the microstructural evolution of directly reduced iron-chromium alloys. This fundamental knowledge is being applied to a process developed at the Georgia Institute of Technology to fabricate metal honeycomb extrusions. A paste composed of oxide powders, binders and lubricants is extruded through a die of the desired cross-section and subsequently reduced to metal with hydrogen. The effects of time, temperature and composition on the extent of reduction and diffusion in reducing Fe2O3-Cr2O3 powder mixtures is investigated. The thermodynamics and kinetics of Fe2O3-Cr2O3 reduction are evaluated in terms of the free energy of formation as well as reducing species. The kinetics of the microstructural changes are evaluated through diffusion measurements. A thermodynamic model for Fe2O3-Cr2O3 was developed and used to determine the maximum amount of Cr2O3 that would reduce when in contact with iron as a function of the ratio . Diffusion studies consisted of Fe-Cr2O3 couples held at temperature in a reducing atmosphere. Cr diffusion in Fe showed a concentration dependence for the geometries investigated.
© EDP Sciences 2004