| The present study is concerned with the microstructural evolution and property improvement of VC/ carbon steel surface-alloyed materials fabricated by high-energy electron-beam irradiation. The mixtures of VC powders and flux (50%MgO-50%CaO or CaF_2) were placed on a plain carbon steel substrate, and then electron beam was irradiated on these mixtures using an electron beam accelerator. The surface-alloyed layers of 1.2∼3 ㎜ in thickness were homogeneously formed without defects, and contained a large amount (up to 10 vol.%) of VC precipitates in the bainitic or martensitic matrix. This microstructural modification including the formation of hard precipitates and hardened matrix in the surface-alloyed layers improved hardness and wear resistance. Particularly in the surface-alloyed material fabricated with the lower input energy density, the wear resistance was greatly enhanced over the steel substrate because of the increased size and volume fraction of VC particles, although the thickness of the surface-alloyed layer decreased. Microstructural modifications including melting, solidification, precipitation, and phase transformation processes of the surface-alloyed layer could also be explained from a thermal transfer modeling and a Fe-V-C ternary phase diagram. |
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