Effect of pulsed magnetic field on retained austenite of quenched 8Cr4Mo4V steel under cryogenic condition

Abstract

High-intensity pulsed magnetic field was applied to modify the microstructure and mechanical propertis of quenched 8Cr4Mo4V bearing steel under the cryogenic environment. The microstructual transformation in 8Cr4Mo4V bearing steel was investigated by X-ray diffraction (XRD), Vibrating sample magnetometer (VSM) and Electron Backscatter Diffraction (EBSD) and so on. The results revealed that individual deep cryogenic treatment (DCT) promote the transformation from retained austenite (RA) in quenched steel to martensite. However, this phase transformation will be inhibited by coupling high-intensity magnetic field with deep cryogenic treatment (MDCT). For instance, the relative reduction of RA content in DCT samples was 10 ± 2%, while that in MDCT samples was 3 ± 3%. Furthermore, the modified Williamson-Hall method was utilized to estimate the dislocation characteristics based on XRD profile analysis. It exhibited that the proportion of edge dislocation significantly decrease from 61.8% to 43.7% by DCT, while this type of dislocation remains almost unchanged after MDCT. Moreover, the microhardness of quenched 8Cr4Mo4V steel became more uniform after MDCT than that of DCT. It can be indicated that the martensite transformation is blocked and carbon cluster is dissolved under the condition of coupling pulsed magnetic field treatment.

Keywords

• Retained austenite
• Pulsed magnetic field
• Cryogenic treatment
• Dislocation characteristics