Investigation of surface crack types under axial compression loading for a case-hardening steel

During cold-forming operations the formability of the materials can be reached due to the low process temperature, leading to crack initiation. For the investigated case-hardening steel 16MnCrS5 longitudinal cracks and shear cracks are identified as the main crack types. The evolution of both crack types is determined by scanning electron microscope (SEM)-investigations and a simplified finite element method (FEM)-model. The results reveal that the initiation point of shear cracks is located at the surface. In contrast thereto longitudinal cracks emanate from second phase particles in the rim zone.