Study on microstructures of pulsed electron beam remelted carbon steel 45

High power density electron beams generated by multiplate pseudospark discharge chamber have been used for bombardments of 45# steel. The transformations of microstructure both on metal surface irradiated by electron beams and along it's lengthways depth have been studied in this paper by SEM and TEM. The results showed that metal surface of bombardment region had been melted quickly, cooled and resolidified abruptly, finally became microcrystalline structure or disordered structure. The section has been divided into melting zone, martensite zone, heat affected zone and base metal. Melting zone was self-quenched under high temperature gradient. Martensite zone and heat affected zone was experienced many times of annealing or tempering processes at the bombardment of multiple pulses so that make crystal grains refined distinctly. The results of microhardness and corrosive resistance showed that mechanical properties of surface layer have been improved due to the refined grain. It is concluded that pulsed electron beam is beneficial to metal surface modification.