M+F dual-phase structures were gained through subcritical quenching in 42CrMo steel. The amount of undissolved ferrite were 0%,3%,10%,15% and 20%, respectively. The effect of undissolved ferrite amount on contact, impact and bending fatigue properties were studied. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons of improving the fatigue life. The experimental results show that the contact, impact and bending fatigue life of M+F dual-phase structure is longer than that of mono-martensite structure. The contact, impact and bending fatigue life elongates with the increase of amounts of undissolved ferrite before the amount of undissolved ferrite reaches 10%. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the contact, impact and bending fatigue life will be the longest.
Journal of Mechanical Strength