Microstructural analysis of vanadium carbide/steel surface-alloyed materials fabricated by high-energy electron-beam irradiation

This study is concerned with the microstructural analysis of vanadium carbide (VC)/steel surface alloyed materials fabricated by high-energy electron-beam irradiation. The mixtures of VC powders and MgO-CaO flux were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these mixtures using an electron-beam accelerator. Microstructures of the irradiated surface regions were examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. Residual pores were found in the specimen processed without flux, but hardly found in the specimens processed with a considerable addition of flux. As a result of irradiation, vanadium content was homogeneously maintained throughout the melted region, and fine vanadium carbides were formed in the melted region. These microstructural modification including the formation of vanadium carbides greatly improved hardness, especially high-temperature hardness up to 500 degreesC.