The influence of hydrogen on very high cycle fatigue properties of high strength spring steel

The influence of hydrogen on very high cycle fatigue (VHCF) properties of high strength spring steel 50CrV4 was studied in this paper. Three groups of specimens with different hydrogen contents (CH) were prepared through different heat treatment procedures: quenched and tempered (specimen QT), annealed at 380 °C in a vacuum after QT (specimen VA), and treated by high-pressure thermal hydrogen charging (HPTHC) after QT (specimen HPTHC). Increase of hydrogen content (CH) was definitely detrimental to the fatigue properties, especially for HPTHC specimens the fatigue strength at 109 cycles decreased considerably. The fatigue limit expression deduced by Murakami was revised in this paper. Basquin exponent was also discussed and it was found that the absolute value of Basquin exponent increases with hydrogen content increasing. Therefore, we could arrive at a conclusion that hydrogen content in steels is a very important factor influencing the VHCF properties of high strength spring steels.