Structure, phase composition and properties of surface layers of the titanium after electroexplosive doping with yttrium and electron-beam processing

Modification of surface layer of technically pure titanium is carried out by the combined method combining electroexplosive doping with yttrium and subsequent irradiation by high-intensity electron beam with parameters as follow: energy density of electron beam-20-70 J/cm2, pulse length-150 μs, number and pulse frequency-3 and 0.3 Hz, respectively. The investigations of elemental and phase compositions, defect substructure, mechanical and tribological characteristics of the doped layer are performed via the contemporary methods of physical materials science (X-ray structural analysis, optical, scanning and transmission electron diffraction microscopies, measurements of microhardness, friction coefficient and wear rate). The formation of multilayer multiphase submicro- and nanocrystalline structure characterized by titanium and yttrium layering is revealed. The 500 nm thick surface layer is amorphous. The 1.0-1.5 μm thick layer is located below and has a columnar structure. Under it, the extended layer (of 20-40 μm) with the structure of dendritic (globular) crystallization is determined. The amorphous layer is enriched with titanium, and the layer with columnar structure lying under it is yttrium-enriched. The main phase of the surface layer is α- yttrium (73% of the volume fraction). The volume fraction of other phases is considerably lesser (α-titanium-10%, carbide TiC and titanium oxide TiO₂-14%, yttrium oxide Y₂O₃-3%). The saturation of titanium surface layer with yttrium, oxygen and carbon atoms results in the formation of metalloceramic layer hardened by oxides and carbides of titanium and yttrium and facilitates the multiple increase in microhardness (more than 3 times as much), reduction of friction coefficient (more than 7 times) and wear rate of modified layer (more than 3 times).