Surface of high-chromium steel modified by an intense pulsed electron beam

The formation of nanostructural multiphase surface layers in high-chromium 12Х18Н10Т and 20Х13 stainless steel under the action of an intense pulsed electron beam in a SOLO system is studied. The Fe–Cr–C system is thermodynamically analyzed. Alloying Fe–Cr alloys with carbon considerably changes their structural and phase state and determines the regions of existence of the carbides M₂₃C₆, M₇C₃, M₃C₂, and M₃C with α and γ phases. The temperature field formed in the surface layer of the steel under the action of the electron beam is numerically calculated. When the energy density of the electron beam is 10 J/cm2, regardless of the pulse length of the electron beam (50–200 μs), the maximum temperature at the sample surface corresponding to the end of the pulse is less than the melting point of the steel. The structure and the mechanical and tribological properties of the surface layer of high-chromium 12Х18Н10Т and 20Х13 steel formed under the action of the intense pulsed electron beam are investigated. It is found that electron-beam treatment of the steel with melting and subsequent high-speed crystallization is accompanied by solution of the initial carbide particles of composition M₂₃C₆—specifically, (Cr, Fe)₂₃C₆—and hence saturation of the crystal lattice in the surface layer with carbon and chromium atoms. In addition, submicronic cells of dendritic crystallization are formed, and nanoparticles of titanium carbide and chromium carbide are deposited. Overall, electron-beam treatment improves the surface and tribological properties of the materials. For 12Х18Н10Т steel, the hardness of the surface layer is increased by a factor of 1.5 and the wear resistance by a factor of 1.5, while the frictional coefficient is decreased by a factor of 1.6. For 20Х13 steel, the microhardness is increased by a factor of 1.5 and the wear resistance by a factor of 3.2, while the frictional coefficient is decreased by a factor of 2.3.