In-situ electron-beam synthesis of boride phases FROM LaB6/Ti system

The paper deals with the direct synthesis of titanum borides from lanthanum hexaboride layers deposited onto a titanium substrate followed by processing with a microsecond low-energy high-current electron beam (LEHCEB). It is shown how the electron-beam energy density affects the structure and properties of the obtained surface layer. The latter consists of 54 to 41 at.% B, depending on the LEHCEB processing mode. Microstructure investigations show that the surface layer is a nanostructured composite consisting of a mixture of TiB and TiB₂ particles distributed in the submicrocrystalline α‑Ti matrix. The boride particle size ranges between 10 and 70 nm, depending on the synthesis modes. It is shown that the formation of the composite nanostructure improves the nanohardness and wear resistance of the synthesized surface layer. When the content of boride phases is the highest, the nanohardness grows up to 12.5 GPa or by 3.9 times, while the wear resistance becomes more than 5 times higher than in the initial titanium substrate.