The influence of minor alloying elements on the properties of stainless steels used for the hot ends of automotive exhaust systems was investigated. The stabilized ferritic stainless steels exhibited intergranular corrosion after certain thermal treatments. The mechanisms of grain boundary sensitization of the stabilized steels were proposed. The difference between precipitation behavior of titanium and niobium carbo-nitrides was examined. Stabilized ferritic stainless steels were subject to intergranular corrosion by thermal treatments that involved dissolution and re-precipitation of carbo-nitrides of stabilizing elements. Titanium-stabilized steels were more prone to intergranular corrosion than niobium-stabilized steels. Plate-like precipitates were formed at the grain boundaries of the sensitized steels. These carbides were identified as Cr-rich M23C6 carbides. It was proposed that niobium is more effective than titanium in preventing the formation of Cr-rich M23C6 carbides at the grain boundaries by forming very small and densely populated carbo-nitrides. The oxidation rates of ferritic stainless steels increased as the titanium content increased but hardly influenced by the change of niobium content. The presence of large cuboid titanium carbo-nitrides were supposed to assist the formation of pores in the chromia scales. (VDEh)
Effects of minor alloying elements on the properties of stainless steels for hot ends of automotive exhaust systems
Einfluss von Mikrolegierungselementen auf die Eigenschaften nichtrostender Stähle für die heißen Enden der Auspuffsysteme von Kraftfahrzeugen
2002
6 Seiten, 12 Bilder, 2 Tabellen, 10 Quellen
Aufsatz (Konferenz)
Englisch
ferritischer nichtrostender Stahl , Fahrzeugausrüstung , Fahrzeugbauteil , Kraftfahrzeugbau , Werkstoffwahl , Mikrolegieren , Konzentrationseinfluss , Mikrogefüge , Abgasschalldämpfer , Abgasanlage , Niobzusatz , Titanzusatz , stabilisierter Stahl , Korrosionsbeständigkeit , Ausscheidungsprodukt , Chrom-Titan-Stahl , Chrom-Niob-Stahl
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