Pulsed Electron Beam Irradiation Research Articles

Влияние водорода на формирование дефектной структуры в сплаве Zr - 1 мас. % Nb при облучении импульсным электронным пучком

Влияние водорода на формирование дефектной структуры в сплаве Zr - 1 мас. % Nb при облучении импульсным электронным пучком

Surface microstructures and high-temperature high-pressure corrosion behavior of N18 zirconium alloy induced by high current pulsed electron beam irradiation

The aim of present paper was to study the microstructural evolution and the high-temperature high-pressure corrosion behavior of N18 zirconium alloy prior and after high-current pulsed electron beam (HCPEB) surface irradiation. Observations of microstructures showed that after HCPEB irradiation, the surface layer of the sample was melted, inside which gradually refined grains, martensites and their internal twin substructures were obtained. Meanwhile, second-phase particles (SPPs) were dissolved into the matrix within the modified layer, and alloying elements Fe, Cr, Nb were supersaturated in Zr-based solid solution. Besides, high residual compressive stress was unceasingly accumulated in the surface layer with the increasing of pulses. After exposed at 500 °C/10.3 MPa superheated steam for 30 days, the corrosion resistance of multiple-pulsed samples, particularly the 25-pulsed one, was obviously higher than that of the initial sample. The combined action of high residual compressive stress, supersaturated alloying elements, selective purification effect and abundant structure defects in the modified layer helped improve the corrosion resistance.

Spheroidisation of metal powder by pulsed electron beam irradiation

A new powder spheroidisation process has been demonstrated using a large-area, pulsed electron beam technique. This was used to dramatically improve the surface morphology of Stellite 6 metal powder. Powder surface asperities up to 20 μm size can be eliminated by melting and incorporation into the near-surface of the particle. Surface finish is significantly improved. Agitation and rotation of particles due to a beam-induced stress wave enables the irradiation of multiples sides of particles, resulting in uniformly smoothed particles after sufficient pulses. Elemental analysis revealed no measurable contamination as a result of the process. Transmission electron microscopy showed a dense layer is produced within a zone up to 3 μm beneath the surface, with a substantially reduced grain size from ca. 2 μm diameter in the bulk to ca. 40 nm. Elemental homogenisation also was accompanied by grain refinement. The irradiated Stellite 6 showed a reduced basic flowability energy (583 mJ compared to 627 mJ for the untreated), explained by reduced particle-particle cohesion and interlocking, and an increased conditioned bulk density of 4.57 g/ml compared to 4.33 g/ml due to satellite/asperity reduction.

Deburring drilled holes in CFRP composites with large pulsed electron beam (LPEB) irradiation

The generation of burrs is one of the most common problems affecting carbon fiber reinforced plastic (CFRP) machining processes. However, it is difficult to develop machining processes that generate no burrs. To overcome the limitations of conventional CFRP composite deburring methods, we propose a new process for deburring drilled holes in CFRP composites based on large pulsed electron beam (LPEB) irradiation. We evaluated the deburring performance as we independently varied the three major controllable parameters that affect energy transfer during LPEB irradiation, namely the acceleration voltage, solenoid voltage, and number of pulses. We optimized the irradiation process to improve the accuracy of the shapes of the holes, and reduced the sizes of the burrs by 97%. We evaluated deviations in the shapes of the holes from perfect circles by measuring their diameters. As our deburring process reduced these deviations by 93%, it significantly improved the dimensional accuracy of the holes. We hypothesize that the deburring mechanism starts with evaporation of the resin that coats the carbon fibers evaporates. This leaves the uncut carbon fibers exposed so that they can be detached by the LPEB irradiation. We obtained high quality, burr-free drilled holes by applying the proposed LPEB deburring method.

Formation mechanism of graphite nanospheres in W-C-Co system under high current pulsed electron beam irradiation

Understanding the formation mechanism of graphite nanospheres (GNS) in W-C-Co system under high current pulsed electron beam (HCPEB) irradiation is necessary for its application on surface modification of WC-Co cemented carbide. With this aim, XRD, SEM, EDS and TEM were used to investigate the effect of HCPEB irradiation on surface microstructure and phase composition. Results showed the micro-WC grains and Co were melted and transformed into nano-grained composite structure in the surface layer ∼1.29 μm. Two general scales of GNS were discerned in two types of element composition ambiences, i.e. ∼100 nm in Co-rich region and ∼50 nm in Co-poor region. Thermodynamic analysis suggested that they were the results of different routes in the non-equilibrium melting and re-solidification process.

Hot corrosion behaviour of thermally sprayed CoCrAlY coating irradiated by high-current pulsed electron beam

Microstructural modifications and hot corrosion behaviour of plasma spraying CoCrAlY coatings before and after high-current pulsed electron beam (HCPEB) irradiation were investigated. The microstructural observations revealed that the coarse surface of plasma spraying CoCrAlY was remelted and changed as a wavy aspect with a compact appearance. The fast heating and melting, and self-quenching effects induced by HCPEB treatment normalized the thermal spraying defects, refined the grains, and changed the elemental distributions. Cyclic hot corrosion test of two kinds of coatings in Na2SO4/K2SO4 (75:25, wt.%/wt.%) eutectic salt was performed at 900 °C in air. After 80 h hot corrosion, the relatively loose and non-protective scale was formed with poor adherence on the initial porous surface, which made the initial coating highly susceptible to hot corrosion. Comparatively, the irradiated coating displayed a stable and slow-growing kinetic curve of very small mass change, revealing that resistance to hot corrosion was superior to that of the initial one. The irradiating effects promoted the formation and self-healing of a dense and adherent Al2O3 scale in the initial stage, which effectively suppressed the formation of internal oxides and sulfides. The results demonstrated that HCPEB technique is an effective way to prolong the service life of MCrAlY coatings.

Nanocrystalline Cr-Ni Alloying Layer Induced by High-Current Pulsed Electron Beam.

In this investigation, chromium (Cr) was adopted as an alloying element on a nickel substrate, and the alloying process was materialized via high-current pulsed electron beam (HCPEB) irradiation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were also conducted for microstructure characterization. The results showed that after HCPEB irradiation a nanocrystalline Cr-Ni alloying layer was formed and numerous dislocations were generated, resulting in a great deal of diffusion paths for Cr elements. Moreover, properties including hardness, wear and electrochemical performance were significantly improved after HCPEB irradiation, which was mainly due to the formation of the nanocrystalline Cr–Ni alloying layer. In addition, each strengthening mechanism that contributed to the hardness of the HCPEB-irradiated sample was mathematically analyzed, and solid solution strengthening was found to be of great importance.

Improved corrosion resistance of Mg alloy AZ31B induced by selective evaporation of Mg using large pulsed electron beam irradiation

Large pulsed electron beam (LPEB) irradiation was employed as a surface treatment of magnesium (Mg) alloy AZ31B to enhance its corrosion and wear resistance. Selective evaporation of Mg induced by LPEB irradiation at an energy density of 5 J/cm2 for 40 cycles has led to the formation of an Al-enriched re-solidified layer with nano-grained structure consisting of Mg3.1Al0.9 metastable phase. The formation of such a re-solidified layer after LPEB irradiation has enabled a decrease in corrosion rate of Mg alloy AZ31B in 3.5% NaCl solution. Different equivalent electrical circuit models were proposed to account for the corrosion behavior of untreated Mg alloy AZ31B and those subjected to LPEB irradiation. A decrease in wear depth when compared to that of the untreated alloy suggests an increase in wear resistance of LPEB-irradiated Mg alloy AZ31B. Adhesive wear is the predominant mechanism of untreated Mg alloy AZ31B while abrasive wear mechanism dominates for LPEB-irradiated Mg alloy AZ31B.

Ibuprofen controlled release from E-beam treated polycaprolactone electrospun scaffolds

Synthetic biodegradable polymers are considered to be a highly suitable materials for the targeted drug delivery devices creating. Especially promising is the use of the electrospinning technique, which makes it possible to obtain materials with a high surface-to-volume ratio that provides active diffusion of the drug into the body tissues. In order to control the rate of polymer degradation and drug release from polymer scaffolds surface modification techniques are widely used. This study was focused on the investigation of ibuprofen-loaded poly (ε-caprolactone) electrospun fibrous scaffolds and modification of theirs surface. Scaffolds with two ibuprofen concentrations were obtained: 5 wt./wt. % and 10 wt./wt.%. The modification was conducted by the pulsed electron beam irradiation. The sustained release of the model drug over a period of one day from both non-treated and treated samples was demonstrated. It was shown, that treatment leads to an increase in drug release rate and does not change surface morphology of scaffolds and fibers diameter distribution.

Surface alloying of high-chromium steel: structure and properties

Here we analyze the structure and mechanical properties of high-chromium steel AISI 420 after combined surface treatment in a single vacuum cycle on the COMPLEX setup through intense pulsed electron beam irradiation of a Zr-Ti-Cu film/steel AISI 420 substrate system and its further nitriding in low-pressure arc plasma at 550 °C for 4 h. The methods of research include scanning and transmission electron diffraction microscopies, X-ray diffraction analysis, and measurements of surface microhardness and wear resistance. The research shows that after pulsed electron beam irradiation, the microhardness of the Zr-Ti-Cu/steel AISI420 system increases by 11%, and its wear resistance by a factor of 3.5. After further nitriding, the hardness of the system increases 2.4 times, and its wear resistances more than 350 times.

Effect of pulsed electron beam irradiation on the grain boundary heterodiffusion in ultrafine-grained molybdenum

Profiles of depth distribution of nickel concentration in the ultrafine-grained molybdenum after isothermal homogenizing annealing and surface irradiation by a pulsed electron beam in a non-melt regime were determined by Auger spectroscopy methods. It was established that the mutual penetration of molybdenum and nickel atoms is activated in the surface layer as a result of electron beam irradiation, and the diffusion regime in the grain boundaries is changed in comparison with that observed under the homogenizing annealing. Indicated changes are shown to be associated with an increase in the dislocation density in the surface layer and the appearance of additional internal stresses caused by the electron beam exposure.

Texturing Effect of Crater-Like Cavities Induced by High-Current Pulsed Electron Beam (HCPEB) Irradiation

High-current pulsed electron beam (HCPEB) irradiation commonly induces crater-like cavities on irradiated surfaces, making them tribologically resemble textured ones. However, the effect of crater-like cavities on the lubricated tribological properties of HCPEB-treated surfaces has not been reported in the literature. This work was aimed at exploring the potential texturing effect of the crater-like cavities. Surfaces with continuous and uniform crater-like cavities were prepared through HCPEB irradiating a 400-nm thick Ta coating that was pre-deposited on polished M50 steel. Their boundary tribological behaviors were studied while sliding in chemically inert, low-viscosity hydrocarbon fuel JP-10 against a Si3N4 ball under 2.0–4.0 GPa. At 2.0 GPa, the coefficient of friction (COF) and wear rate of the polished M50 steel were above 0.16 on average, with large fluctuation, and 1.49 × 10−5 mm3/N·m (a rectangle-like profile of 167.9 μm × 8.1 μm), respectively. In comparison, the HCPEB-treated Ta coating had a stable, marginally fluctuant COF of 0.11 and a near-zero wear rate. Under other higher loads, the HCPEB-treated Ta coating still exhibited a stable COF of 0.11 on average with small fluctuation, and its wear track width was only half that of the M50 steel. The analysis of the wear topographies indicates that the substantial reduction in both the COF and wear rate was mainly due to the texturing effect originating from the crater-like cavities.

Two step porosification of biomimetic thin-film hydroxyapatite/alpha-tri calcium phosphate coatings by pulsed electron beam irradiation

Here we show a new and effective methodology for rapid/controllable porosification of thin-film ceramics, which may be applied in medical devices/electronics and membrane nano-filtration. Dense hydroxyapatite applied to Ti6Al4V by plasma-assisted PVD was electron-beam irradiated to induce flash melting/boiling. Deposited coatings contained amorphous and nano-crystalline/stoichiometric hydroxyapatite (~35 nm). Irradiation (voltages 13–29 kV) led to ablation (up to 45% mass loss) and average/maximum pore areas from (0.07–1.66)/(0.69–92.53) μm2, mimicking the human cortical bone. Vitrification above 1150 °C formed (~62–30 nm) crystallites of α-Tri Calcium Phosphate. Unique porosification resulted from irradiation-induced sub-surface boiling and limited thermal conductivity of hydroxyapatite, causing material to expand/explode through the more quickly solidified top surface. Commercially applicable, roughened Ti6Al4V exacerbated the heating and boiling explosion phenomenon in certain regions, producing an array of pore sizes. Scaffold-like morphologies were generated by interconnection of micron/sub-micron porosity, showing great potential for facile generation of a biomimetic surface treatment for osseointegration.

Transient oxidation behavior of MCrAlY coating irradiated by high-current pulsed electron beam

The surface microstructure of air plasma spraying (APS) CoCrAlY coatings deposited on the Ni-based superalloy before and after high-current pulsed electron beam (HCPEB) irradiation was characterized by using scanning electron microscope (SEM) and transmission electron microscope (TEM). After HCPEB irradiation, the rough surface of APS-CoCrAlY was remelted and changed as ‘hill and valley’ aspect with a compact appearance. Besides, the thermally sprayed defects including rough surface, porosities, microcracks and etc were removed. In addition to the usual nano-grains, the HCPEB treatment has induced deformed structures containing Y-Al oxide particles within the remelted layer. Transient oxidation tests were carried out. As for the APS-CoCrAlY, a continuous thermally grown oxide (TGO) protective layer was not formed, and mixed oxides were instead formed on the surface due to its high roughness, the presence of structural defects and chemical heterogeneities. Comparatively, as for the HCPEB-CoCrAlY, a complete and dense α-Al2O3 layer was formed rapidly in the remelted surface due to the irradiated effects during the transient oxidation process, which guaranteed a protective effect on the bond coat for further oxidation behavior.

Surface composite microstructure and improved mechanical property of YG10X cemented carbide induced by high current pulsed electron beam irradiation

The surface microstructure evolution and its effect on mechanical property was systematically investigated for YG10X cemented carbide irradiated by high current pulsed electron beam (HCPEB) with a steady energy density of 6 J/cm2 and different pulse numbers. The surface morphology was characterized by optical microscopy (OM), three-dimensional laser scanning microscopy (LSM) and scanning electron microscopy (SEM); and energy dispersive spectrometry (EDS) and X-ray diffractometry (XRD) was carried out to reveal the elemental profile and phase transformation under HCPEB irradiation. During the HCPEB-induced rapid re-melting and re-solidification process, the redistribution of chemical elements, grain refinement and phase transformation WC(hex) → graphite + β-WC1-x(fcc) occurred. Moreover, the preferential precipitation of nano-grained graphite in the Co-rich region of melt pool was discovered. The drastic structural change led to a maximum ~34% increment of the initial state in microhardness and about a two third reduction in friction coefficient.

Cross-sectional analysis of the graded microstructure and residual stress distribution in a TiNi alloy treated with low energy high-current pulsed electron beam

A Ti-(55.08wt.%)Ni shape memory alloy (SMA) having a grain size of 30 μm, was subjected to low-energy high-current pulsed electron beam (HCPEB) irradiation with parameters: pulse duration τ = 2−2.5 μs, maximum electron energy 25 keV, energy density ES = 3.8 ± 0.7 J/cm2; beam diameter of ∼ 60 mm, number of pulses n = 32. Microstructure modifications, a value and distribution of residual stress induced by HCPEB treatment were investigated in detail. XRD and cross-sectional TEM/EDS/SAED analysis were used for microstructural characterization of the TiNi samples before and after HCPEB treatment. As a result, the HCPEB-modified TiNi surface layer consists of four successive sublayers differing in phase composition, type of texture and defect substructure. In total, the thickness of the HCPEB-modified TiNi surface layer is, at least, 10 μm. Based on the XRD and nanoindentation data, the dependences of residual stress values on the depth from the irradiated surface in the HCPEB-modified TiNi surface layer were estimated and plotted. The values and sings of the stress components in perpendicular (σI⊥) and parallel (σI||) directions to the TiNi sample surface were calculated: σI⊥ <0, σI||>0. The gradient of residual stress values is preserved in the HCPEB-modified TiNi surface layer: from ∼ 800 MPa (in absolute value) near the irradiation surface to ∼ 220 MPa at a depth of about ∼ 10 μm. The residual stress fields are localized in the near-surface layer I and sublayer III with different type of B2-structure. Their relaxation occurs in the sublayer II by means of the stress-induced В2 → R martensitic transformation.

Dynamics of Surface Heating and Quenching of Titanium by a Submillisecond Intense Electron Beam

The paper presents measurements taken with a high-speed infrared pyrometer for the surface temperature of VT1-0 titanium alloy during pulsed electron beam irradiation at different pulse energy densities. Also presented are numerical simulation data on thermal fields for the same conditions, showing a good agreement with the measurements. The results demonstrate that the heating rate of the VT1-0 surface depends on the main beam parameters, and its solidification occurs at a temperature ≈ 280 °C lower than the melting point.

Surface modification of AISI 1045 steel by pseudospark based pulsed electron beam

In this paper, the surface modification of AISI 1045 steel by a hollow cathode discharge (HCD) based pulsed electron beam and the formation of the surface microstructure via a short time duration of the pulsed beam treatment are the main focus under investigation. The electron beam in our work is generated by a compact HCD electron beam device named pseudospark discharge, which is characterized by the fast plasma ignition and quenching rates. And the surface microstructure, composition and microstructure crystallographic information of AISI 1045 steel pre and post pseudospark based pulsed electron beam modification are investigated by using metallographic microscope, scanning electron microscope (SEM), X ray diffraction (XRD) and Electron Back Scatter Diffraction Patterns (EBSD). The experimental results demonstrate that a microstructure consisting of cementite and C-supersaturated austenite is formed in the near-surface region after the pseudospark based pulsed electron beam irradiation. Both the phenomenon of the metal target grain refinement and the mechanism of the grain refinement evolution are investigated by a diversity of diagnostic methods. It is also showed that the material surface modification process is highly dependent on the transient properties of the HCD-based pulsed electron beams, which offers a new and effective method to improve the performances of the metallic material surface microstructure and other properties.

Effect of high current pulsed electron beam surface irradiation on the microstructure and electrochemical behavior of zircaloy-4

Abstract The microstructure and electrochemical behavior of zircaloy-4 prior and after high-current pulsed electron beam (HCPEB) irradiation were investigated. The microstructures of the surface layer were studied by means of X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Observation results indicated that, martensitic phase transformation was induced by HCPEB irradiation and formed plate martensitic structures containing a high density of ultrafine twins. When the number of pulse was increased, these structures were constantly refined along with their parent β grains. Besides, second-phase particles (SPPs) in the modified layers were completely dissolved into the substrate and formed Fe, Cr-containing supersaturated solid solution. The electrochemical behavior was characterized by using electrode impedance spectroscopy (EIS) and potentiodynamic polarization curves. Electrochemical results demonstrated that, compared to the initial specimen, all the irradiated specimens showed better corrosion resistance in 0.01 mol LiOH solution, among which 25-pulsed specimen possessed the best corrosion resistance. Surface selective purification, supersaturated Fe, Cr elements in substrate and abundant structure defects jointly promoted the improvement of the corrosion resistance.

Surface alloying of gray cast iron with chromium by high current pulsed electron beam treatment

To improve the surface properties of gray cast iron (GCI), chromium coating was deposited on the GCI surface treated by high current pulsed electron beam (HCPEB) irradiation. Microstructures of the modified layer were characterized by means of XRD, OM and SEM. Results show that with the increasing number of HCPEB pulses, the graphite was gradually dissolved and the alloying layer with thickness of 5 ∼ 11 μm was obtained. Besides, martensitic structures and refined austenite grains were also formed after HCPEB alloying. Results of the performance test show that the surface microhardness, wear and corrosion resistance of alloying samples were significantly improved after HCPEB alloying treatment.