Microstructure and Properties of High Current Pulsed Electron Beam Surface Alloying on 20 Steel

To improve the surface properties of 20 steel, the chromium element was alloyed on 20 steel by high current pulsed electron beam (HCPEB) with pre-coating to obtain a high quality of alloyed layers. Microstructure and properties of the alloying layer were studied by means of XRD, OM, SEM, TEM and multi-purpose microcomputer electrochemistry analyzer. The results show that, after HCPEB alloying, the formation of an alloyed layer with the depth of about 4-6 mu m on the surface is observed. The solid solution and diffusion of Cr element occurs on the surface of the substrate. Bending and granulating occur on part of cementite under bending stress induced by HCPEB irradiation, the C atoms generated by the dissolution of the cementite combine with the chromium to form a small amount of nanograined carbide Cr23C6. After HCPEB alloying, the surface microhardness increases by 35% and corrosion current density reduces one order of magnitude than original sample.