Very High Cycle Fatigue Properties of Automotive High Strength Spring Steel 50CrV4

This paper investigates very high cycle fatigue(VHCF) properties of high strength spring steel-50CrV4 with USF-2000 ultrasonic fatigue testing,and then fatigue fractographs are observed by Quanta600 scanning electron microscope(SEM).Results show that fatigue cracks are all initiated from internal and subsurface inclusions,and the composition of inclusions are mainly oxides of calcium and aluminium,which is analyzed by energy dispersive X-ray spectrometer(EDXS).The size of inclusions measured are all larger than the size of critical inclusion,so in this experiment we don't observe ODA around inclusion on the fatigue fracture surfaces.Fatigue limit exists in 109 cycles regime,and S-N curve is a traditional fatigue limit model.