Effect of Microstructure on Exhaust Manifold Cracks Produced From SiMo Ductile Iron

Ductile cast irons are used as high temperature materials in internal combustion engines, because they are microstructurally stable at high operating temperatures. SiMo granular graphite cast irons contain Fe(2) MoC and M(6) C carbide precipitates due to their higher concentration of both silicon and molybdenum. The microstructure of these cast irons consists of carbides dispersed within the ferrite matrix. The microstructural change and the crack formation mechanism in manifolds produced from SiMo ductile iron are studied. Chemical analysis, optical and scanning electron microscope studies have been completed and evaluated.