Crack nucleation propagation in wear-resistant bainite ductile cast iron

Crack nucleation and propagation in wear-resistant bainite ductile cast iron were investigated by the press trace method and SEM. The results indicated that cracks nucleated mainly in the interface of graphite-matrix and in the interface of carbide-matrix, and the former case is easier to happen. But the nucleation mechanisms were different. The graphite nodular, as a hole of the matrix for its low shear modulus, will attract dislocations other than to hinder them. Thus it will decrease the elastic energy of the dislocations. The cracks nucleated in the other side of the interface of graphite-matrix, which is far away from the dislocations, along the direction of dislocation motion. But carbide will hinder the movement of the dislocations, and the cracks nucleated in the front side of the interface of carbide-matrix. The cracks propagated along the interface path forward and were analyzed in thermodynamic aspects.