Abstract
AnnotationThe work is devoted to the structural-phase analysis of steels of the austenitic and martensitic grade, irradiated with a high-intensity pulsed electron beam of the submillisecond duration of exposure in the mode of the surface layer melting. A thermodynamic analysis of phase transformations occurring during heat treatment in alloys of the composition Fe-Cr-C and Fe-Cr-Ni-C, which are the basis of steels 20X13 and 12X18H10T, is carried out. It is shown that formation of solid solutions on the basis of α-iron (BCC crystalline lattice) and γ- iron (FCC crystalline lattice) as well as the entire range of carbide phases of a complex elemental composition (M23C6, M7C3 и M3C, where symbol M refers to atoms of metallic elements Fe, Cr, and Ni) is possible in equilibrium conditions in given materials. The irradiation of steels 12X18H10T and 20X13 with a high-intensity pulsed electron beam of the submillisecond duration of exposure is carried out. It is shown that the electron-beam processing of steel in the melting mode and the subsequent rapid crystallization is accompanied by a significant transformation of the surface layer structure, consisting in complete dissolution of original carbide phase particles; in formation of dendritic crystallization cells of submicron sizes; in occurrence of martensitic γ→α and γ→ϵ transformation; in re-allocation of nanosized particles of carbide and intermetallic phases.
Highlights
The development of new volume-doped materials, which are still the main way to improve the reliability and the longevity of details of mechanisms and machines, is becoming increasingly problematic due to the scarcity and the high cost of doping elements
It is shown that the electron-beam processing of steel in the melting mode and the subsequent rapid crystallization is accompanied by a significant transformation of the surface layer structure, consisting in complete dissolution of original carbide phase particles; in formation of dendritic crystallization cells of submicron sizes; in occurrence of martensitic α and transformation; in re-allocation of nanosized particles of carbide and intermetallic phases
Crystalline lattice) and -iron (FCC crystalline lattice) and the entire range of carbide phases of a complex elemental composition (M23С6, M7С3 and M3С where the symbol M refers to atoms of metallic elements Fe, Cr, and Ni)
Summary
The development of new volume-doped materials, which are still the main way to improve the reliability and the longevity of details of mechanisms and machines, is becoming increasingly problematic due to the scarcity and the high cost of doping elements. It is economically and technically feasible to develop a fundamentally different approach to the development of materials when the mechanical strength of the part is achieved by using cost-effective, workable low-alloy steels, and special surface properties by a solid or a local formation of relatively thin doped layers, or by depositing coating with properties that meet performance requirements. Generated layers have a metallurgical bond to the substrate with adhesion at a level of cohesion, and insignificantly change the dimensions of the item
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