Solidification of SiMo Nodular Cast Iron for High Temperature Applications

During the 1960s and 70s research was aimed at developing a material withstanding the ever higher temperatures in a combustion engine. This work resulted in what have later been named SiMo and D5S. SiMo is a nodular cast iron typically containing 4-6 % Si and 0.5-2 % Mo and can be used in temperatures up to 850-860 A degrees C. D5S is a nickel base material. High silicon and silicon-molybdenum content improves the dimensional stability of ductile iron. Silicon increases the transformation temperature where austenite transforms to ferrite. Molybdenum partly segregates and freezes in intercellular regions, promoting carbides while during the solid state transformation molybdenum particles precipitate around grain boundaries. The solidified material shows a range of interesting structures and phases which will be presented.