Ultrasonic fatigue testing of cast steel G42CrMo4 at elevated temperatures

The fatigue life of cast steel G42CrMo4 in two different heat treatment conditions was investigated at room temperature (RT), 473 K and 773 K up to the range of very high cycle fatigue (VHCF), that is, 10(9)cycles. The fatigue life is determined by casting defects, the hardness of the steel matrix and by temperature. Fatigue life data were discussed in correlation with crack-initiating defects analysed on fracture surfaces. The SN curves obtained at RT and at 473 K show a large scatter. However, the SN curve at 773 K exhibits a larger slope parameter and a significantly reduced scatter. It is shown that the fatigue behaviour of the cast steel G42CrMo4 changes from 473 to 773 K in the range of VHCF. The fatigue lives of the specimens tested at 773 K were described with a crack growth model.