Surface hardening alloy VT6 of electroexplosion alloying with boron carbide and by electron beam treatment

Investigations aimed at identifying the changes in the surface layer of titanium alloy VT6 after combined treatment are carried out. Combined surface treatment of titanium alloy VT6 includes alloying with plasma formed during electrical explosion of titanium foil with a powder weight quantity of boron carbide and subsequent irradiation by high-intensity pulse electronic beam of sub millisecond exposure time. The titanium foil is used as exploded conductor during electroexplosive alloying. A weight quantity of boron carbide powder is placed into explosion area over the titanium foil. The laboratory electroexplosive device EVU 60/10 is used for EEA (electroexplosive alloying).The main parameters for a pulse liquid-phase alloying are set by the value of the charging voltage of the energy storage device of the accelerator, the diameter of the nozzle channel and the distance from its section to the sample. Subsequent thermal treatment of the titanium alloy VT6 surface layer is performed with high-intensity pulse electronic beam at the SOLO device (Institute of High Current Electronics SB RAS). The study found that electroexplosive alloying of the surface layer of titanium alloy VT6 samples leads to the formation of the highly developed relief. In the surface layer a heterogeneous distribution of alloying elements is observed through the methods of electron scanning microscopy. A significant difference in its concentration in the revealed layers leads to the difference in its strength and tribological properties. The subsequent electron beam treatment of the alloyed surface leads to its smoothing. The formation of the multilayer structure occurs and the distribution of alloying elements in the surface layer becomes more uniform. Analysis of the treated surface irradiated by the electron beam revealed the presence of two characteristic elements of the structure, formed in the result of the subsequent treatment with high-intensity pulse electron beam. The first structure element is acicular structure areas with the needle size of 1-10 microns. Studies of the transverse sections of the titanium alloy after combined treatment allowed to determine the thickness of the modified layer, which is not more than 30 μm. So, we can conclude that electroexplosive alloying and fast cooling at pulse treatment lead to the formation of a structure of submicro-nanoscale level that can improve the strength and tribological properties of the treated surface.

titanium, boron carbide, electric explosion alloying electron-beam treatment, structural-phase states