Influence of the graphite elements morphology on the fatigue crack propagation mechanisms in a ferritic ductile cast iron

Ductile cast irons (DCIs) are commonly considered as really interesting materials, due to their interesting combination of mechanical properties and technological peculiarities. Characterized by the high castability that is a cast irons technological peculiarity, DCIs are characterized by a very interesting combination of good mechanical properties (e.g., tensile strength and fatigue resistance). These properties are strongly influenced by the DCIs microstructure, that is defined both by the matrix (considering the morphological peculiarities like phases distribution, grain dimension, etc.) and by the graphite nodules elements, that are characterized by shape, dimension and distribution. In addition, the presence of defects (like pores, both micro and macro) can strongly affect the DCIs mechanical behaviour (e.g., considering large castings). In this work, a ferritic DCI with degenerated nodules was obtained and the fatigue crack propagation resistance was investigated by means of fatigue crack propagation tests and compared with the behaviour of a commercial ferritic DCIs.