Fatigue crack propagation and overload damaging micromechanisms in a ferritic–pearlitic ductile cast iron

Recently discovered (1948), ductile cast irons (DCIs) are able to combine the good castability of grey irons with the interesting mechanical properties, both static and cyclic, of carbon steels, allowing to directly produce components with complex shape that are requested to be characterized by high mechanical performances, especially considering toughness and fatigue resistance. DCIs mechanical properties and damaging micromechanisms depend on the matrix (ferritic, pearlitic, ferrite pearlitic, ausferritic, etc.) and on the graphite nodules morphological peculiarities (shape, dimension, distribution, etc.). In this work, the fatigue-crack propagation micromechanisms in a ferritic–pearlitic DCI were investigated, focusing both the role played by the microstructure and the contribution of the graphite nodules. In addition, the overload effects on the composite microstructure of the investigated ferritic–pearlitic DCI were analysed.