The relationship between inclusions characteristic parameters and bending fatigue performance of 20Cr2Ni4A gear steel

• The bending fatigue life of 20Cr2Ni4A steel is given by drawing P-S-N curve. • The failure modes caused by inclusions are modeled and classified. • The life prediction model is established with three parameters of inclusion. Common heavy-duty 20Cr2Ni4A gear steel is widely used in industrial systems, but there are still problems with its use, such as materials processing issues and a short fatigue life during use. These drawbacks prevent 20Cr2Ni4A from meeting the quality requirements for heavy-duty gear steel in modern industrial systems. Therefore, in practical engineering application, the fatigue life of steel will be predicted to ensure that the fatigue failure of gear steel will not occur in the normal service process. By analysis of the bending fatigue process of structural steel, researchers found that almost every failure is closely related to the size, location and mechanical state of inclusions in the steel. Therefore, in order to accurately characterize the impact of inclusions on fatigue performance, we first used ASPEX inclusion field detection instrument and nanoindentation analyser to make statistics of all inclusions in the two steels, and the contents, distribution, average size and mechanical properties of inclusions in 20Cr2Ni4A steel were accurately counted. Subsequently, the bending fatigue life of two differently processed steels was tested, and a P-S-N curve was drawn. Then, the fatigue fracture was analysed and four fatigue fracture models were summarized to determine the influence of inclusions in the fatigue process. Based on the models by Nisha S, the effects of the number, area, and types of the inclusions were added as corrections, and a new set of life prediction models was proposed. The model was verified by experiments, and the results have a high accuracy. Thus, this approach can be applied to the prediction of the fatigue life of 20Cr2Ni4A steel.