Anomalous Expansion of Stainless Steel Foil for Metal Honeycomb Catalytic Converter Induced by High-Temperature Oxidation

Abstract

High-temperature oxidation behavior of γ-Al₂O₃ slurry coated Fe-20Cr-5Al based thin foil (50μm in thickness) for a catalytic converter has been investigated. An anomalous foil expansion during high-temperature oxidation was observed in a case that the γ-Al₂O₃ slurry contains Ce³⁺ or La³⁺ or Y³⁺. The expansion was accelerated by minor additives to the stainless steel foil such as Nb, Ti, Ta, or Mo. On the other hand, the expansion was effectively suppressed by a small addition of rare-earth elements or yttrium to the stainless steel foil. It has been concluded that the foil expansion was resulted from a creep deformation by a compressive stress which is accumulated in the course of lateral growth of α-Al₂O₃ scale formed between the foil and the coated layer.