Influence of casting skin on the fatigue lifetime of ferritic ductile cast iron

Abstract

The fatigue behavior of cast iron is usually investigated on machined specimens. Components of cast iron, however, have a casting skin. Therefore, the investigation of the influence of the casting skin on the lifetime is of interest. To study this influence, isothermal fatigue tests were carried out on heat resisting spheroidal graphite cast iron EN GJS SiMo 4.05 in 4-point bending setup at 400 °C. Specimens with and without casting skin were investigated comparatively. The number of cycles to failure was significantly lower for specimens with casting skin. Metallographic investigations underline the reduction of lifetime caused by casting skin.

Strain-Controlled Fatigue Behavior of a Nodular Cast Iron in Real Off-Highway Axles: Effects of Casting Skin and Strain Ratio

“…Another relevant microstructural feature in nodular cast iron components is the casting skin, which represents the rim zone of the casting and can lead to a detrimental effect on the fatigue strength, not only for the high surface roughness but also for the deviating microstructure, since discontinuities such as inhomogeneous microstructures (e.g., decarburization or graphite degeneration and a ferritic or pearlitic rim, imperfections, pores, defects, and/or sand inclusions coming from the mold) are typically concentrated there [2]. The influence of the casting skin on the fatigue strength of cast iron components has been widely investigated in the recent literature [9,[17][18][19][20][21][22][23][24][25]. This effect must be accounted for in the fatigue design of components where machining is not needed, such as the case of axles of off-highway vehicles.…”