Abstract
Quench cracks became a challenge in large serial production of martensitic components. The geometry is simple, and concentrations of stresses from the geometry itself were not indicated by numerical simulation. Grain boundary ferrite is presented in the component surface from where the cracks start. An example from another application is interesting to consider; titanium grade 5. Grain boundary alpha on prior beta grain boundaries is not accepted for aerospace applications. The volume for plastic deformation in the phases along the grain boundaries is restricted. The ductile part of the fracture indicates forces from unbalanced quenching and elevated temperature at time of crack start. The general focus for improvement will be overcritical surface temperature, vapor phase break and mix of turbulent/lamellar flow. More effective quenching around the whole component is, in this case, assumed to be better than slower quenching.
