The investigation results of elemental and phase composition, state of defective substructure and microhardness of the surface layer of «film (Ti)/substrate (SiC-ceramics)» system (Ti film 0.5 μm ...thick was deposited on the surface of SiC-ceramics) subjected to treatment with an intense pulsed low-energy electron beam (15 J/cm2, 200 μs, 0.3 s−1, 20 pulses) are presented. It is shown that irradiation of the «film (Ti)/substrate (SiC-ceramics)» system with an electron beam is accompanied by the formation of multielement multiphase (SiC; TiC; Ti5Si3) surface layer having submicro- and nanocrystalline structure. Microhardness of the irradiated surface layer reaches a value of 74 GPa, that is twice the value of microhardness of SiC-ceramics (36 GPa).
The purpose of the present studies is to establish the formation patterns of the structure and properties of the surface layer of 060A35 steel modified using a combined method that includes plasma ...spraying of a powder coating and the subsequent irradiation with an intense pulsed electron beam. Plasma spraying on the surface of a steel powder of the system Ni-Cr-B-Si (PGSR-4 with a fraction of 80-100 μm) was performed on the original installation equipped with two plasma generators. The irradiation of the modified steel layer was carried out with an intense pulsed electron beam on the installation SOLO. The investigation of the phase and elemental composition, the state of the defective substructure were carried out using methods of X-ray phase analysis, optical and scanning electron microscopy. The mechanical properties of the irradiated surface were characterized by microhardness. It is shown that plasma spraying of a powder coating leads to formation of a high-relief surface containing micro- and macropores. The subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the surface layer with Ni, Cr, B and Si atoms, formation of dendritic crystallization cells of submicron sizes, release of nanoscale particles of the second phase, formation of a quenching structure. Together, this has allowed to increase the microhardness of the modified layer in 4.6-6.5 times.
The presence and behavior of a gas–metal interfacial layer at the free surface of shock-wave driven flying vehicles in gases of various compositions and densities has not been sufficiently studied so ...far. We present new comparative data on “dusting” from the free surface of lead into vacuum and gas as dependent on the surface roughness, pressure amplitude at the shock-wave front, and phase state of the material. Methods of estimating the mass flux of ejected particles in the presence of a gas medium at the free metal surface are proposed.
A heterodyne interferometer is used photon Doppler velocimetry (PDV) method to study a particle discharge from the free surface of lead samples of different roughness under a shock-wave load. In ...experiments, the velocity of the free surface of samples and the dust flow velocity are determined, and indicator foils and thin glasses are used to calculate the specific weight of the dust. Dependences of the specific weight of particles on their relative velocity are constructed. Effects of roughness and phase state of the substance after a shock-wave load on the possibilities to determine the velocity of the free surface and the specific weight of discharged particles using indicator foils are analyzed. It is shown that, with given surface roughness, the specific weight of dust, discharged from the surface during lead melting under the action of a shock wave or load wave, is much larger than in a sample being in a solid state.
Structural-phase state of gradient structures obtained in the course of additive electron-beam production, friction-stir treatment and hybrid additive-thermomechanical technology was investigated by ...optical and scanning electron microscopy. Characteristic features of defect formation in materials obtained by additive method are revealed. The peculiarities of defects "healing" in additive materials after friction-stir treatment are determined. In tensile tests the mechanical properties of the samples before and after further post-treatment in aluminum alloys are measured.
Nitrolysis of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetracyclo-5.5.0.0
3,11
.0
5,9
dodecane results in the substitution of benzyl groups by the nitro groups with the formation of ...2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo5.5.0.0
3,11
.0
5,9
-dodecane. The reaction sequentially proceeds through the nitration of the benzyl groups predominantly at
para
-position, the substitution of one nitrobenzyl group with the nitro group, and the introduction of the second nitro group into the nitrobenzyl fragment. The replacement of the remaining dinitrobenzyl fragment is a more difficult process, which reaches completion only by the end of the nitration. Another reaction product is
p
-nitrobenzoic acid, which is formed in the secondary reactions. No substitution of a
p
-nitrobenzoyl group with the nitro group takes place in the nitration of 2,6,8,12-tetraacetyl-4,10-di(
p
-nitrobenzoyl)-2,4,6,8,10,12-hexaazatetracyclo5.5.0.0
3,11
.0
5,9
dodecane under similar conditions.
The results of investigation of phase and elemental compositions, defect substructure states, mechanical and tribological properties of the modified surface of Steel Gr1 are presented. The process of ...modification consists in plasma spraying of a Ni–Cr–B–Si-based powder coating followed by its irradiation with a high-intensity pulsed electron beam. It is shown that the coating surface formed by plasma spraying contains micro- and macro-pores and is characterized by high relief. A subsequent processing of the modified surface with a highintensity pulsed electron beam of a submillisecond duration in the mode of surface layer melting is accompanied by smoothing of the coating surface, saturation of the surface layer crystal lattice with Ni, Cr, B and Si atoms, formation of submicron cells of dendritic recrystallization, precipitation of nanosized particles of the second phase, and formation of quench structure. When combined, these treatments result in the formation of a hardened layer up to 1500 μm in thickness, whose microhardness and wear resistance by 4.6–6.5 and 4 factors exceed the respective characteristics of the initial steel.
Using transmission and scanning electron microscopy, a pulsed intense electron beam irradiation of a sintered boron carbide ceramic is shown to lead to the formation of a modified surface layer with ...a nonporous polycrystalline structure and initiate microtwinning and the formation of extended submicron- and nanocrystalline interlayers along the boundaries of boron carbide crystallites. The observed structural changes lead to an increase in the fatigue life of the modified layer.
Particles are discharged from surfaces of materials under a shock-wave load. Experimental results on determining the minimal values of a specific weight of particles with which their velocity can be ...detected using a heterodyne interferometer photon Doppler velocimetry (PDV) method are presented. An effect of multiple frequency shift of a Doppler signal in the case of laser radiation being reflected from surfaces of materials and a semitransparent layer of dust particles is described.
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