Very-High-Cycle Fatigue Performance of High-Carbon–Chromium Bearing Steel With Different Hydrogen Contents

The very-high-cycle fatigue (VHCF) behavior of a high-carbon–chromium bearing steel with different hydrogen contents was investigated using ultrasonic fatigue testing. The results show that the VHCF property of the vacuum heat–treated sample VA with 0.29 ppm H is comparable to that of the air heat–treated one NH with 0.38 ppm H, while it was significantly reduced for the electrochemically hydrogen charged sample CH with 1.69 ppm H, a decrease of fatigue strength at 10⁹ cycles by ~20%. An increase in hydrogen content exhibited noticeable influence on decreasing the size of granular bright facet (GBF), a special area around crack initiator, at identical applied stress amplitude, and the threshold values for the beginning of GBF formation and stable crack growth. A parameter taking into account the effect of hydrogen to Murakami's $\sqrt{\text{area}}$ parameter model could well estimate the fatigue strength.