Evaluation of Fatigue Strength of Ductile Cast Iron Composed of Ferrite-pearlitic Structures with As-cast Surfaces: Effect of Surface Roughness, Microstructure Transition Layers, Defects and Residual Stress on Fatigue Strength

In order to elucidate the complex effects of surface roughness, the transition of microstructures from the surface to the interior, defects and residual stress, tension-compression fatigue tests have been conducted by using shot blasted ferrite-pearlite ductile cast irons with as-cast surfaces. Regardless of the applied stress levels, the fracture origins of the specimens were mostly situated at a defect near an as-cast surface, slag, or pinhole at Nf