Microstructure, Wear Resistance, and Fracture Properties of (TiC, SiC)/Ti-6Al-4V Surface Composites Fabricated by High-Energy Electron Beam Irradiation (Part 2. Wear and Fracture Properties)

摘要

The present study aimed at investigating hardness, wear properties, and fracture toughness of (TiC, SiC)/Ti-6Al-4V surface composites fabricated by high-energy electron beam irradiation. A large amount (30 approx 66 vol. percent) of precipitates such as TiC and Ti_5Si_3 improved the hardness and wear resistance of the surface composite layer two times and six to twenty five times, respectively, greater than that of the substrate. Particularly in the surface composite fabricated with TiC and SiC powders, the selective wear of the matrix and the cracking or fallen-offs of precipitates were considerably reduced because it had a network-shaped structure of abundant TiC and Ti_5Si_3 precipitates, thereby leading to the best hardness and wear resistance. Observation of the microfracture process of the surface composite layers revealed that microcracks were primarily initiated at precipitates, and that shear bands were formed in the matrix between these microcracks. Thus, fracture toughness was determined mainly by the volume fraction of precipitates working as fracture initiation sites and partly by the matrix property interrupting the crack propagation. These findings suggested that the high-energy electron beam irradiation method was economical and useful for the development of titanium-base surface composites with improved hardness and wear properties.