An Investigation of Heat Treatment Residual Stress of Type I, II, III for 8Cr4Mo4V Steel Bearing Ring Using FEA-CPFEM-GPA Method

The heat treatment residual stress of 8Cr4Mo4V steel bearings seriously affects the contact fatigue life. The micro stress concentration at the carbide interface leads to the initiation of micro cracks. Therefore, in this paper, the systematic analysis of heat treatment residual stress of 8Cr4Mo4V steel is conducted. FEA was used to analyze the residual stress of type I after heat treatment process. Based on numerical simulation and EBSD results, CPFEM was carried out to study the distribution of type II residual stress. Using high-resolution characterization results, GPA was performed to study type III residual stress caused by crystal defects. The FEA results indicate that thermal strain and phase transformation strain dominate the macroscopic stress change before and after martensitic transformation. During the first tempering process, the phase transformation leads to the release of quenching residual stress. The large stress concentration at the carbide interface is revealed by CPFEM. High-resolution characterization of coherent interface between carbide and matrix reveals that the micro residual strain at this interface is small. Through a systematic analysis of the residual stress of 8Cr4Mo4V steel, a basis is provided for modifying the macroscopic and microscopic residual stress of heat treatment to improve the bearing performance.