Surface modification of 5CrMnMo steel with continuous scanning electron beam process

Surface modification is an important component of improving mechanical properties in mold manufacturing. In this work we present a method for surface modification on 5CrMnMo mold steel with continuous scanning electron beam. The surface morphology and microstructure of the processed samples have been investigated by the three-dimensional measuring laser microscope and scanning electron microscope respectively. The changes in the surface roughness, microhardness and wear resistance before and after electron beam treatment were also examined. The variation regularity of surface roughness and microhardness under the changes of beam current was found. Comparing with the initial samples, at a beam current of 7 mA, the roughness decreased from 2.23 μm to 0.90 μm, while the hardness increased from 355 HV to 656 HV. The wear resistance of modified layer was improved remarkably compared with the initial state. Additionally, the composite microstructure of acicular and lath martensites were obtained by the martensitic transformation occurring in the modified layer. The samples which were irradiated by electron beam contained three areas as follows: melted layer, heated affected zone and substrate matrix.