There is a wide spectrum of cast ferrous heat resistant alloysavailable for exhaust component applications such as exhaustmanifolds and turbocharger housings. Generally speaking, theferrous alloys can be divided into four groups including:ferritic cast irons, austenitic cast irons, ferritic stainless steels,and austenitic stainless steels. Selection of a suitable alloyusually depends on a number of material properties meetingthe requirements of a specific application. Ferritic cast ironscontinue to be an important alloy for exhaust manifolds andturbocharger housings due to their relatively low cost. Abetter understanding of the alloying effects and graphitemorphologies of ferritic cast irons are discussed and theireffect on material behavior such as the brittleness at mediumtemperatures is provided. The nickel-alloyed austenitic castirons, also known as Ni-resist, exhibit stable structure andimproved high-temperature strength compared to the ferriticcast irons. Austenitic cast irons with varying nickel contentswere evaluated in terms of microstructure stability, heattreatment, oxidation and thermal fatigue resistance. For themost demanding applications requiring even higher elevated-temperature strength, creep, and fatigue resistance, ferritic oraustenitic stainless steels may be selected. The chemicalcomposition, microstructures, and properties of cast stainlesssteels are reviewed. Synthesizing this information on materialbehavior provides a guide to aid in the selection of ferrousalloys for high temperature applications.
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