Metallic honeycomb structures are used as catalyst substrates in automotive exhaust gas systems. This application requires an outstanding corrosion resistance at elevated temperatures of the substrate material and of the brazed joints.
Improvements can be achieved by the use of rapidly solidified foils as substrate material and as brazing materials for the substrate structures, respectively. For the substrate material, which is a rolled Fe-22%Cr-5% A1 foil at present, a drastic improvement of the lifetime in a higher temperature corrosion environment results from a significant increase of the aluminum content up to about 12% which can be realized by rapid solidification. This and other features of the rapidly solidified Fe-Cr-A1 ribbons will be discussed with respect to the prospects for the application.
The dosage of brazes can be essentially simplified by the use of ductile brazing foils. In the case of using standardized brazing alloys as amorphous foils, a drastic degradation of the corrosion resistance of the substrate material results. Therefore, an adapted alloy development has been performed optimizing corrosion and flow behaviour. Data of the resulting Ni-Nb-Si brazing foils will be presented.