Improvement of the Hardness and Wear Resistance of (TiC, TiN)/Ti-6A1-4V Surface-Alloyed Materials Fabricated by High-Energy Electron-Beam Irradiation

摘要

This study is concerned with the microstructural analysis and improvement of the hardness and wear resistance of Ti-6A1-4V surface-alloyed materials fabricated by a high-energy electron beam. The mixtures of TiC, TiN, or TiC + TiN powders and CaF_2 flux were deposited on a Ti-6A1-4V substrate, and then the electron beam was irradiated on these mixtures. In the specimens processed with a flux addition, the surface-alloyed layers of 1 mm in thickness were homogeneously formed without defects and contained a large amount (over 30 vol pct) of precipitates such as TiC, TiN, (Ti_xAl_(1-x))N, and Ti(C_xN_(1-x)) in the martensitic or N-rich acicular alpha-Ti matrix. This microstructural modification, including the formation of hard precipitates and hardened matrices in the surface-alloyed layers, improved the hardness and wear resistance. Particularly in the surface-alloyed material fabricated by the deposition of TiN powders, the wear resistance was greatly enhanced to a level 10 times higher than that of the Ti alloy substrate. These findings suggested that surface alloying using high-energy electron-beam irradiation was economical and useful for the development of titanium-based surface-alloyed materials with improved hardness and wear resistance.