High chromium steel modification by the intense discrete electron beam: Structure and properties

The Fe-Cr-C system thermodynamic analysis has been made. It has been demonstrated that the Fe-Cr alloys carbon alloy addition results in the significant structural-phase state change in them and exerts determinant influence on the M₂₃С₆, M₇С₃, M₃С₂ and M₃С carbides existence domain by the α-and γ-phases. The temperature field numerical calculations, forming in the steel superficial layer in the case of the electron beam irradiation, have been carried out. It has been demonstrated that the peak temperature, being achieved on the sample surface towards the end of the impulse effect, is below steel melting temperature at electrons beam energy density 10 J/cm² regardless of the electrons beam pulse duration (50-200 ms). The peak temperature on the irradiation surface is equal to the steel boiling temperature at electrons beam energy density (20-30) J/cm² and at pulse duration 50 µs. The peak temperature on the irradiation surface achieves and increases the steel melting temperature at pulse duration 200 µs. The AISI 321 and AISI 420 steel surface irradiation has been carried out by the intense pulse electron beam. The studies have been made and the nanostructured polyphaser superficial layers formation laws analysis have been done. It has been established that the steel electronic-beam treatment is accompanied by the М₂₃С₆ ((Cr, Fe,)₂₃C₆) composition initial carbide phase particles solution, by the carbon and chromium atoms superficial layer crystal lattice saturation, by the submicron sizes and dendritic crystallization cells formation, by the titanium carbide and chromium carbide nano-sized particles abstraction. The mechanical and tribological tests of the AISI 321 and AISI 420 steel samples, irradiated by the intense pulse electron beam, have been done. It has been detected that the superficial layer hardness increases in 1.5 times and the superficial layer wear resistance increases in 1.5 times. The friction coefficient decreases in 1.6 times. The microhardness increases in 1.5 times. The wear resistance increases in 3.2 times. The friction coefficient reduces in 2.3 times.