Correlation of microstructure with the hardness and wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation

Abstract

The correlation of microstructure with the hardness and wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron-beam irradiation was investigated in this study. The mixtures of TiC, SiC, or TiC + SiC powders and CaF2 flux were placed on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures using an electron-beam accelerator. The surface composite layers of 1.2 to 2.1 mm in thickness were formed without defects and contained a large amount (up to 66 vol pet) of precipitates such as TiC and Ti5Si3 in the martensitic matrix. This microstructural modification, including the formation of hard precipitates and a hardened matrix in the surface composite layer, improved the hardness and wear resistance. Particularly in the surface composite fabricated with TiC + SiC powders, the wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy substrate, because 66 Vol pet of TiC and Ti5Si3 was precipitated homogeneously in the hardened martensitic matrix. These findings suggested that high-energy electron-beam irradiation was useful for the development of Ti-based surface composites with improved hardness and wear properties.