New FeCrAl Alloys for Diesel Engine Catalytic Converters 2004-01-1491

This paper describes new FeCrAl alloys for metallic catalytic converter substrates used in heavy-duty diesel engines. The new alloys contain 11∼16 wt% Cr and 5∼7 wt% Al without addition of Y, Hf or rare earth elements. The maximum services temperature of these alloys, by design, is 800°C. The new alloys were made by roll bonding and diffusion alloying. A thin layer of aluminum was bonded to both sides of a stainless steel strip to obtain a three layer Al/Stainless Steel/Al composite foil. The aluminum was then diffused into the stainless steel during a diffusion alloying process to form a FeCrAl alloy. Diffusion alloying can be achieved either in foil processing or during metallic substrate converter fabrication. The brazing process typically used for metallic substrate converters is well suited for in-situ diffusion alloying. Tests showed that the new alloys at the required foil thickness have room temperature mechanical properties similar to existing FeCrAl alloys, possess excellent semi-cyclic oxidation resistance at the maximum in-service temperature (800°C), and can be fabricated into honeycomb-like metallic catalytic converters using current manufacturing methods of corrugating, winding and brazing.