Effect of alternating magnetic field on microstructure evolution and mechanical properties of M50 bearing steel during tempering process

Abstract

The effect of alternating magnetic field (AMF) on the microstructure evolution and mechanical properties during tempering of M50 bearing steel have been investigated for evaluating the application prospect of magnetic field in steels. Microstructural observation and EDS analysis shows that during solidification process, M2C carbides rich in molybdenum are easily formed on the matrix of M50 bearing steel. Microstructure characterization results show that the application of AMF promotes the dissolution and refinement of carbides. At medium tempering temperature (300 °C, 380 °C), Vickers hardness increased with the application of AMF. Furthermore, due to the occurrence of secondary hardening, the Vickers hardness increases at high tempering temperature of 540 °C and the application of AMF has little effect on the hardness change. In addition, tensile fracture morphology observation shows that the morphology is mainly quasi-cleavage fracture. At medium tempering temperature, the presence of large carbides and transgranular cracks on the matrix results in the low tensile strength. For the high tempering temperature, the AMF could significantly reduce the carbide size and increase the tensile strength. This provides a new idea for improving the mechanical properties of M50 bearing steel by using AMF during tempering process.

Keywords

• Tempering
• Magnetic field
• Bearing steel
• Carbide
• Mechanical property