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MoDification of strUctUre anD sUrface ProPerties of hyPoeUtectic silUMin By intense PUlse electron BeaMs Methods of contemporary physical materials science are applied for the analysis of structural and phase states, tribological and mechanical properties of hypoeutectic silumin treated by electron beams with parameters as follow: energy density-10-35 j/cm 2 , pulse duration-10 µs, number of pulses-3, pulse-repetition frequency-0.3 Hz. The initial structure of silumin comprises grains of aluminiumbased solid solution, eutectic grains, inclusions of silicon and intermetallic compounds with different shapes and sizes. Electron beam treatment (EBT) with energy density of 20-35 j/cm 2 causes melting of the surface layer, dissolution of silicon in clusions and intermetallic compounds. A structure of high-speed cellular crystallization is formed, and submicro-and nanosize particles of the second phase are reprecipitated. An average size of crystallization cells are of 0.3-0.5 µm at the irradiated surface and of 0.4-0.8 µm on the lower edge of the layer with the cellular structure. The graded structure and phase states are analysed at a depth of up to 120 µm. The submicron grains of lamellar eutectic are detected at a depth of 15 µm. The lateral sizes of eutectic lamellae are within the range of 25-50 nm. The study indicates that nanohardness of irradiated silumin changes nonmonotonously and reaches its maximum at a depth of about 30 µm, which is approximately four times higher than hardness in the initial state. Hardness of the layer close to the irradiated surface (that is at a depth of ≈ 5 µm) is higher by a factor of ≈ 1.6 than that of

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ProsPects for the aPPlication of surface treatMent of alloys By electron BeaMs in state-of-the-art technologies recent papers on the application of intense pulsed electron beams for surface treatment of metals, alloys, metalloceramic and ceramic materials are reviewed. The advantages of pulsed electron beam application as compared with laser beams, plasma flows, ion beams are mentioned. Promising trends of the electron-beam processing application are analysed: (1) the surface smoothing, the elimination of surface microcracks with simultaneous change in structural-phase state of the surface layer for creating the high production technologies of finishing treatment of critical metal products of intricate shape from Ti-6Al-4V alloy and titanium, steels of different classes, WC-10 wt.% Co hard alloy, aluminium; (2) the removal of microburrs being formed in manufacturing of precision moulds (SKD11 steel) and biomedical materials (Ti-6Al-4V alloy); (3) the finishing surface treatment of moulds and dies; (4) the improvement of functional properties of metallic biomaterials: stainless steel, titanium and its alloys, the titanium-nickelide-based alloys possessing the shape memory effect, magnesium alloys; (5) the treatment of medical materials and implants; (6) the formation of surface alloys for powerful electrodynamic systems; (7) the improvement of characteristics of aircraft engine and compressor blades; (8) the formation of thermobarrier coatings being applied to combustionchamber surface; (9) the increase in fatigue service life of steels and alloys; (10) the hardening of rails' tread surface. As shown, at a correct selection of process parame

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Abstract. Structure-phase state and tribological properties of the coating deposited on Hardox 450 martensitic low-carbon steel by flux-cored wire Fe-C-Cr-Nb-W and modified by subsequent electron-beam processing were studied. It is shown that the electron beam processing of ~ 5 mm thick deposited layer leads to the formation of ~ 20 µm thick modified surface layer with the main phases of α-Fe and NbC, Fe3C and M6C(Fe3W3C) carbides. Wear resistance of the weld layer is 70 times higher than the one of the original steel. IntroductionThe production of coatings with high service properties making possible the increase in service durability of the articles in the extreme conditions of high wear, corrosion, mechanical loads and temperatures is the important fundamental problem. The thorough analysis of the relation «wear parameters -hardness -microstructure» is necessary in scientific and practical use of various kinds of surfacing in the critical articles. Only in this case it is possible to produce the articles with high service parameters [1 -8].The purpose of the research is the analysis of structure and tribological properties of the layer formed on Hardox 450 steel by electrocontact surfacing of powder wire of system Fe-C-Cr-Nb-W and modified by high intensity pulsed electron beam irradiation.Hardox 450 steel (weight %): (0.19-0.26 C; 0.70 Si; 1.6 Mn; 0.025 P; 0.010 S; 0.25 Cr; 0.25 Mo; 0.004 B; balance -Fe) was used as a test material. The surfaced electrode 1.6 mm in diameter had the following chemical composition (weight %): 1.3 C; 7.0 Cr; 8.5 Nb; 1.4 W; 0.9 Mn; 1.1 Si, balance -Fe.The testing techniques of the surfacing by methods of modern physical material science are presented in [1].

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