Yttrium alumina-forming alloys

Work on one particular ferritic steel, Fecralloy, for fabrication of catalyst substrates was pioneered by the United Kingdom Atomic Energy Authority at Harwell and Johnson Matthey, in collaboration with Resistalloy, which developed technology for producing thin strip [32]. This and related alloys, in addition to iron, chromium, and aluminum, contain low levels of elements such as yttrium (0.1-3.0%), thought to enhance the protective properties of the surface alumina layer. Alumina forms by the oxidation of bulk... 

In general, both cordierite and metallic monoliths are unsuitable as catalytic supports. To process a monolith into an active monolithic catalyst, a layer of porous catalytic support must be deposited on the walls between channels. y-Alumina appeared to be the most effective support for automotive catalysts. The alumina layer is deposited by sol-gel technique (so called washcoating). Adherence of 7-alumina to cordierite is relatively strong. However, to form the stable 7-alumina layer on a metallic surface, we need to use an appropriate alloy that is appropriately processed before the layer is deposited. Stainless steel containing chromium, aluminum, and yttrium subjected to thermal treatment under oxidizing conditions meets requirements of automotive converters. Aluminum in the steel is oxidized to form 7-alumina needles (whiskers) protruding above the metal... 

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