Team 20 - High Temperature Cast Iron Materials for Exhaust Components

Diesel engine exhaust environments create a harsh setting for components due to the combined effects of high temperatures, thermal cycling, corrosive gases, particulate matter, and demanding mechanical loads. Cast irons are widely used in these conditions because they are relatively inexpensive and easy to manufacture compared to alternatives such as titanium or superalloys. Casting also provides economic advantages by allowing complex geometries to be produced without extensive welding or machining. To withstand the severe exhaust environment, high-temperature ductile cast irons, particularly silicon molybdenum (SiMo) alloys, are commonly used in exhaust systems and other engine components. Compared to other cast ferrous materials, ductile iron offers a beneficial combination of strength, ductility, and toughness due to its nodular graphite microstructure, which enhances flexibility and impact resistance. In contrast, white iron is extremely hard and brittle with high wear resistance and compressive strength because its carbon exists as hard carbides, while grey iron is more brittle but provides excellent vibration damping because of its flake graphite structure. Although SiMo ductile irons exhibit improved performance at elevated temperatures, the effects of alloy composition, heat treatment, and casting parameters on their microstructure and mechanical properties are not yet fully understood. This project aims to evaluate these factors to determine the optimal alloy compositions and processing conditions, providing Caterpillar with data and guidance for the selection and production of ductile iron components designed for high-temperature service.