Study Of Surface Alloying On Iron Carbon Alloy By High Current Pulsed Electron Beam

In recent years,the steel is currently one of the most widely used engineering materials,it is important for the development of world industry to use the surface alloying technology to strengthen the surface properties and extend the service life of steel.In the study,the chromium element was alloyed on 20# steel,45# steel,cast iron by High Current Pulsed Electron Beam(HCPEB)to improve the overall surface properties.The surface and cross section morphologies and the phase components before and after the HCPEB treatment was investigated by the optical microscope(OM),the scanning electron microscope(SEM),the transmission electron microscopy(TEM)and the X-ray diffraction(XRD).The surface and cross-section hardness of the samples before and after the alloying treatment were measured by using a Vickers durometer and the corrosion resistance of the samples before and after the alloying treatment was measured using an electrochemical workstation.The influence mechanism of pulse numbers,carbon content,and the effect of surface alloying was established by analyzing the change of the surface microstructure and the properties of the samples under different pulse numbers and different materials.The experimental results showed that: after HCPEB treatment,the "melting pit" morphology was showed on the surface of 20#steel and 45#steel.It was worth noting that,the surface of the 20#steel sample was more uniform and smooth than that of the 45# steel.The formation of an alloyed layer with the depth of about 4~9?m on the surface of two materials was observed,and the solid solution and diffusion of Cr occurred on the surface of the substrate,the Cr element combined with the C atoms generated by the dissolution of the cementite to form a small amount of nanograined carbide Cr23C6.It showed that the microhardness of two materials were increased after the HCPEB treatment.In addition,the surface microhardness of 45 # steel increased more than that of 20# steel samples.The corrosion resistance of 20# steel and 45 steel samples was significantly improved by HCPEB irradiation alloying,and the corrosion resistance of 20# steel was improved obviously.After surface alloying treatments by HCPEB,the crater morphology was formed on the modified surface of the cast iron,at the same time,the surface graphite had obvious cracking and dissolution.The formation of an alloyed layer with the depth of about 5-11?m on the surface of the cast iron was observed,the alloying layer was composed of the remelting layer and the Cr diffusion layer.The solid solution and diffusion of Cr element occurred on the surface of the substrate.The C atoms generated by the dissolution of the graphite combine with the chromium to form a small amount of nanograined carbide Cr23C6.After HCPEB alloying,with the increase of pulses numbers,the microhardness of the surface layer of cast iron was greatly improved.The effect of the HCPEB alloying on the cast iron material was poor in improving the corrosion resistance,there was only a slight increase under the irradiation of high pulse was observed.The surface roughness,the uniformity of the surface layer,and the solid solution of Cr elements all determined the corrosion resistance of the samples.