Liquid-Phase Boriding of High-Chromium Steel

The structural-phase states and tribological properties of 12Kh18N10T steel subjected to electroexplosive alloying (EPA) with titanium and boron and subsequent electron-beam processing in various modes in terms of the energy density of the electron beam and the duration of the exposure pulse have been analyzed using methods of modern physical materials science. It has been established that EPA of steel with titanium and boron leads to the formation of a surface layer with multiphase submicro-nanocrystalline structure, characterized by the presence of micropores, microcracks, and microcraters. Complex processing, combining EPA and subsequent irradiation with high-intensity pulsed electron beams, leads to the formation of 60-μm-thick multiphase submicro-nanocrystalline surface layer. It is shown that the phase composition of a surface layer of steel is determined by the mass ratio of titanium and boron during electroexplosive alloying. The microhardness of a modified layer is defined by the relative mass fraction of titanium borides in the surface layer and can be more than 18 times higher than the microhardness of steel in its initial state (before electroexplosive alloying). Modes of complex processing have been determined at which the surface layer containing exclusively titanium borides and intermetallic compounds based on titanium and iron is formed. The maximum (approximately 82% by weight) titanium boride content is observed when steel is processed in a regime with the highest mass of boron powder in the sample (m_B = 87.5 mg; m_Ti/m_B = 5.202). With a decrease in mass of boron powder, the relative content of borides in the surface layer of steel decreases. It was found that integrated processing of steel is accompanied by a sevenfold increase in microhardness of the surface layer and wear resistance of the steel increases by more than nine times.