Effect of High-Current Pulsed Electron Beam Processing of Zr-1%Nb Alloy on Its Oxidation Kinetics at 1200C in Air and Steam

The paper reports the effect of high-current pulsed electron beam (HCPEB) processing of the Zr-1%Nb alloy, as one of the most widely used in water-cooled nuclear reactors, on the kinetics of its oxidation at 1200 °C in air and steam (these conditions are typical for potential loss-of-coolant accidents). It was shown that HCPEB processing caused a change in the surface morphology of the samples. In particular, craters with diameters of about 100 μm were found on the modified surfaces. They had initiated at an energy density of 5 J/cm2 and were characterized by relevant reliefs with microcracks. After HCPEB processing at 10 J/cm2, the craters were deeper with fractured surface layers. In addition, a pronounced surface relief corresponding to quenched martensitic microstructures was observed on the modified sample surfaces that had formed due to high heating and cooling rates. Due to sufficient degradation of the sample surfaces after HCPEB processing at 10 J/cm2, the kinetics of high-temperature oxidation was estimated only for the as-received samples and ones treated at 5 J/cm2. It was found that the as-received samples showed slightly greater weight gain levels in both air and steam environments, which fully correlated with the thickness ratio of the oxide, α-Zr(O) and prior-β layers. These phenomena and further research directions were discussed.

Structure and mechanical properties of stainless-steel specimens, made by additive method, after pulsed electron beam treatment

The article presents a method for finishing the surface of metal products made by sequential electron-beam surfacing, which consists in modifying the surface with an intense low-energy electron beam of submillisecond duration. On the example of 308LSi stainless steel, the results of such processing are demonstrated, the optimal modes of exposure are determined. It is shown that as a result of pulsed electron-beam processing, a homogeneous polycrystalline structure without cracks is formed on the surface with unchanged, relative to the initial material, elemental composition, strength (microhardness) and tribological (wear rate) properties. In this case, the surface roughness is reduced to 2.1 times in the longitudinal direction relative to the surfacing plane, to 5.2 times in the transverse direction. Tensile tests of specimens showed anisotropy of mechanical properties depending on the direction of tension relative to the surfacing plane, which decreases after surface pulse electron-beam processing.

Synthesis of MAX-phases, structure and phase composition of modified layers on titanium alloy VT-1 as a result of electron-beam treatment

The article presents the results of research and identification of optimal conditions of formation of MAX-phases during treatment of titanium alloy VT-1 by an electron beam in a vacuum. The study of strength characteristics, thermal properties of composite layers was carried out. Thermodynamic study of phase equilibrium in Ti-Si-C and Ti-B-C systems under high vacuum conditions was carried out in order to optimize conditions of formation of functional layers. A mathematical model of the thermal impact of a powerful fast-moving electron beam on the surface of a titanium alloy has been developed VT-1 under the conditions of electron beam processing in the framework of the theory of thermal conductivity using the COMSOL Multiphysics software complex. The obtained numerical results made it possible to investigate the regularity of the distribution of temperatures and their rates of change depending on the action of the electron beam.

Electron-Beam Surface Modification of Boron-Based Diffusion Layers Obtained of the Surface of Steel H21

In recent years the interest in the development of new protective coatings with improved functional properties for machine parts’ surface have been of great fundamental and applied importance. The current study is devoted to the creation of coatings based on boron and aluminium on the surface of alloy steel using a cutting-edge method, combining thermal-chemical treatment (TCT) and subsequent electron beam processing (EBP). TCT was carried out in treatment pastes based on boron carbide and aluminum at 950°C and 1050°C for 2 hours. As a result of processing, diffusion layers with a thickness of up to 120 μm and 580 μm were formed on the steel surface after TCT at 950°C and 1050°C respectively. The subsequent EBP led to a complete transformation of the primary diffusion layer and an increase in its thickness to 1.6 mm. XRD analysis showed significant differences in composition before and after EBP: new compound, such as tungsten borides (WB, W2B9) and iron boride (Fe2B) were detected. In addition, it was determined that the distribution of microhardness and elemental composition (B, Al, W) over the layer thickness after EBP had a more favorable profile without significant fluctuations compared to the sample after TCT. The concentration of Al decreased significantly after EBP. It dropped from 18% after TCT to a low of 1%.

Generation of increased mechanical properties of Cantor high­entropy alloy

The article considers a brief review of the last years of Russian and foreign research on the possibilities of improving mechanical properties of the Cantor quinary high­entropy alloy (HEA) with different phase composition in wide temperature range. The alloy, one of the frst created equimolar HEAs with FCC structure, needs mechanical properties improvement in accordance with possible felds of application in spite of its high impact toughness and increased creep resistance. It has been noted that bimodal distribution of the grains by sizes under severe plastic torsional strain at high pressure of 7.8 GPa of cast alloy and subsequent short­time annealing at 873 and 973 K can change strength and plastic properties. Nanodimensional scale of the grains surrounded by amorphous envelope has been obtained for HEA produced by the method of magnetron sputtering and subsequent annealing at 573 K. In such a two­phase alloy nanohardness amounted to 9.44 GPa and elasticity modulus – to 183 GPa. Using plasticity effect induced by phase transformation in (CrMnFeCoNi)50Fe50 alloy obtained by the method of laser additive technology the ultimate strength of 415 – 470 MPa has been reached at high level of plasticity up to 77 %. It has been ensured by FCC → BCC diffusionless transformation. It is shown that difference in mechanisms of plastic strain of cast alloy at 77 K and 293 K (dislocation glide and twinning) determines a combination of increased “strength­plasticity” properties. Samples for generation of twins prestrained at 77 K exhibit increased strength and plasticity under subsequent loading at 293 K in comparison with the unstrained ones. For HEA obtained by laser additive technology this way of increasing properties is also true. The way of improving mechanical properties at the expense of electron beam processing is noted. The attention is paid to the necessity of taking into account the role of entropy, crystal lattice distortions, short­range order, weak diffusion and “cocktail” effect in the analysis of mechanical properties.

Towards the Possibility of Additive Manufacturing of XNA-Based Devices Using Molecular Engineering Principles

This paper considers a novel approach for integration between molecular engineering of XNA-based structures and additive manufacturing of XNA-based devices based on multiparametric characterization of XNAs by different functional descriptors (such as physical properties of XNA-based materials and precursors of XNA-based molecular devices) and the possibility of thermal or electron-beam processing as a prerequisite of the industrial technical process development for such device implementation. This can be performed in the framework of additive manufacturing by connecting the output of the XNA synthesizer or nucleic acid synthesizer with 3D-printer nozzles in such a way that oligos / AGCTX products are supported into the nozzles separately.