Surface microstructures and improved mechanical property of 40CrMn steel induced by continuous scanning electron beam process.

• The surface modification of 40CrMn steel is carried out by continuous scanning electron beam process. • The method of ring scanning surface treatment by continuous electron beam is proposed. • Explore the effects of process parameters on surface morphology, microstructure, microhardness and wear resistance. • The mechanical properties of 40CrMn steel were improved significantly after electron beam treatment. Continuous scanning electron beam process (CSEBP) was conducted on 40CrMn steel to enhance its mechanical properties. The influence of electron beam process parameters on the surface microstructures and mechanical properties of 40CrMn steel was investigated. The result shows that the cross-section of the sample after CSEBP contained three districts as follows: melted layer, heated affected zone and substrate. At a beam current of 5 mA, the surface microhardness increased from 309.7 HV to 692.8 HV, which was in 2.34 times of the substrate hardness. Additionally, the surface microhardness decreased nonlinearly with the increase of electron gun moving speed. At a moving speed of 120 mm/min, the surface microhardness reached a maximum value of 666.2 HV. At a moving speed of 300 mm/min, the surface roughness reduced from 1.754 μm to 0.801 μm. The wear loss of the samples after scanning electron beam treatment decreased significantly compared with the initial samples. [ABSTRACT FROM AUTHOR]