| This study aimed at improving hardness by tempering of VC/carbon steel surface-alloyed material fabricated by high-energy electron-beam irradiation. The mixture of VC powders and flux (50%MgO-50%CaO) was placed on a plain carbon steel substrate, and then electron beam was irradiated on this mixture using an electron beam accelerator. The surface-alloyed layer of 1.8 mm in thickness was homogeneously formed without defects. The microstructural analysis indicated that VC particles were coarsely formed along solidification cell boundaries, and the matrix inside cells was mostly composed of lath-type martensite and fine cuboidal VC particles. A large amount (10.1 vol.%) of these VC particles in the lath-type martensitic matrix improved hardness four times greater than that of the substrate. When the VC/steel surface alloyed material was tempered, a number of fine VC particles were precipitated in, the tempered martensitic matrix, thereby leading to the additional hardness improvement. Therefore, the hardness of the surface-alloyed layer was further enhanced by tempering, while the residual stress in the layer could be removed and the fracture toughness could be increased. |
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