Large Pulsed Electron Beam Research Articles

Improvement of tool life via unique surface modification of a tungsten carbide tool using a large pulsed electron beam in Ti-6Al-4V machining

The surface quality of a cutting tool is an important factor for determining machinability performance. This paper proposes a new approach to improve the tool surface quality using large pulsed electron beam (LPEB) irradiation. LPEB irradiation is a process that enhances the mechanical characteristics of substrate surfaces. In this study, the effects of LPEB irradiation on a tungsten carbide tool were evaluated over the acceleration voltage range of 10 to 40 keV. Surface modification of the cutting tool was analyzed in terms of the tool's material constituents, mechanical properties, edge roundness, and surface roughness. LPEB irradiation at 30 keV modified the cobalt and carbon contents of the tool surface, thus improving hardness, compressive strength, and tool surface roughness. The machinability of the LPEB-treated cutting tool was investigated based on the tool wear by performing an orthogonal cutting experiment of Ti-6Al-4V. After treatment with 30 keV LPEB irradiation, the tool wear was reduced; specifically, the flank wear length was reduced by up to 64.6 %, compared to the untreated cutting tool. An examination of the 30 keV irradiated machined material surface and the chip morphology showed substantial reductions in the surface roughness and friction coefficient, by 56.5 % and 31.2 %, respectively, compared with the untreated condition.

Effect of a large pulsed electron beam (LPEB) irradiation on mechanical properties and fatigue behavior of Ti-6Al-4V

Effect of a large pulsed electron beam (LPEB) irradiation on mechanical properties and fatigue behavior of Ti-6Al-4V

A delamination prevention of tetrahedral amorphous carbon (ta-C) coating using large pulsed electron beam (LPEB) pretreatment

The tetrahedral amorphous carbon (ta-C) coating is one of the fascinating surface coating for superior mechanical properties. Although its outstanding mechanical strength, it is hard to achieve adhesion stability due to high interfacial and residual stresses. Here, we introduce a new concept of pretreatment called large pulsed electron beam (LPEB) treatment. To specify the adhesion of the ta-C coating following the LPEB treatment, various adhesion tests, including the scratch test and Rockwell indentation test, were conducted. Thus, the ta-C coating pretreated with LPEB was found to have excellent adhesion through qualitative and quantitative analyses. Furthermore, to elucidate the mechanism for improving adhesion, analyses were conducted from two aspects: 1) deformation of the substrate and 2) stress change at the interface between the coating and the substrate. As a result, ta-C pretreated with LPEB increased the hardness of the substrate and supported the coating well. In addition, the thermal contraction of the coating was decreased after deposition, reducing the stress between the coating and the interface, and the adhesion was considerably improved.

Waterproof and Wear-Resistant Surface Treatment on Printed Parts of Polyamide 12 (PA12) by Selective Laser Sintering Using a Large Pulsed Electron Beam

Waterproof and Wear-Resistant Surface Treatment on Printed Parts of Polyamide 12 (PA12) by Selective Laser Sintering Using a Large Pulsed Electron Beam

Deep-Sintered Copper Tracks for Thermal Oxidation Resistance Using Large Pulsed Electron Beam.

Thermal oxidation resistance is an important property in printed electronics for sustaining electrical conductivity for long time and/or under harsh environments such as high temperature. This study reports the fabrication of copper nanoparticles (CuNPs)-based conductive tracks using large pulsed electron beam (LPEB) by irradiation on CuNPs to be sintered. With an acceleration voltage of 11 kV, the LPEB irradiation induced deep-sintering of CuNPs so that the sintered CuNPs exhibited bulk-like electrical conductivity. Consequently, the sintered Cu tracks maintained high electrical conductivity at 220 °C without using any thermal oxidation protection additive, such as silver, carbon nanotube, and graphene. In contrast, the films irradiated with an acceleration voltage of 8 kV and irradiated by intense pulsed light (IPL) showed fast oxidation characteristics and a corresponding reduction of electrical conductivities under high temperatures owing to a thin sintered layer. The performance of highly thermal oxidation-resistant Cu films sintered by LPEB irradiations was demonstrated through the device performance of a Joule heater.

Corrosion Enhancement of the AISI 304 Stainless Steel Using a High Power Diode Laser and Large Pulsed Electron Beam

The large pulsed electron beam (LPEB) has been widely used for surface modification of metals, alloys, polymers and composites due to its unique interaction mechanisms with materials. Especially for metals, it can simultaneously improve mechanical characteristics and chemical stabilities during rapid melting and re-solidification processes inducing a phase transformation at the re-solidified layer. However, generation of craters has been reported to adversely affect surface quality. It is important to reduce the craters following the LPEB irradiation for the effective protection of pitting corrosion on the surface of stainless steels. In this study, a hybrid surface modification method using a high power diode laser (HPDL) and LPEB is proposed to reduce the generation of craters during the LPEB irradiations. The size and density of craters generated during the LPEB irradiations were effectively reduced following the hybrid surface treatment using HPDL. The corrosion resistance was significantly improved by reducing craters and phase transformation. The passive region on the re-solidified layer after the HPDL-assisted LPEB irradiation showed much wider range comparing to the bare surface of stainless steels. Furthermore, the pitting potential was also significantly modified from less than 0 mV/SCE to over 800 mV/SCE following the hybrid irradiations. After the corrosion tests, the depth of corroded pits was also significantly reduced by 75 % after the hybrid surface modification. To conclude, the HPDL-assisted LPEB irradiation has resulted in superior surface profile and improved pitting corrosion resistance as well as the general corrosion resistance following the elimination of non-metallic inclusions on the surface.

Enhancement of the surface properties of selective laser melted maraging steel by large pulsed electron-beam irradiation

The present work aimed to decrease the surface roughness of maraging steel (MS) by selective laser melting (SLM) using large pulsed electron-beam (LPEB) irradiation as a post-treatment. The MS samples were fabricated using different combinations of laser power, scanning speed, hatch distance, and build angle. The morphological features, surface roughness, phase content, and corrosion resistance of the MS samples in their as-fabricated (ASF) state were compared after LPEB irradiation. The ASF SLM-MS samples exhibit the presence of partially melted particles that spread over the entire surface and many cracks in both the longitudinal and transverse directions. A higher arithmetical mean height (Sa: 2−17 μm), large variations in Sa measured at various locations, and a strong dependence of Sa on build angle were also observed. Post-treatment by LPEB irradiation removed the partially melted particles, while reflow of the molten mass filled the cracks and voids and facilitated the formation of a uniform surface with a bright metallic finish. This has resulted in a significant decrease in Sa (0.50–4.50 μm) and a smaller variation in Sa measured at different locations. Body-centered cubic α-martensite was the predominant phase for the ASF SLM-MS samples, along with a small fraction face-centered cubic γ-austenite phase. After LPEB irradiation, the martensite was reverted to the austenite phase. The corrosion resistance of the LPEB-irradiated samples was moderately better than that of the ASF SLM-MS samples. The uniform surface morphology, removal of partially melted particles, absence of pores and cracks, decrease in Sa, and moderate improvement in corrosion resistance suggests that LPEB irradiation can be used as a post-treatment for SLM-MS samples.

Reducing the pitting susceptibility of AISI 304 stainless steel using a hybrid treatment of high-power diode laser and large pulsed electron beam irradiation

Large pulsed electron beam (LPEB) irradiation has been widely used for surface modification of metals, alloys, polymers, and composites due to its unique interaction mechanisms with materials. The rapid melting and resolidification processes during LPEB irradiation induce phase transformation at the resolidified layer, which enables a simultaneous improvement in mechanical characteristics and chemical stability of metals. However, the generation of craters during LPEB irradiation adversely affects surface quality. It is imperative to minimize crater formation following LPEB irradiation to mitigate pitting corrosion on the surface of stainless steel (SS). In this study, a hybrid surface modification approach using a high-power diode laser (HPDL) and LPEB is proposed to reduce the crater generation during LPEB irradiation. The size and density of craters generated during LPEB irradiation were effectively reduced following the HPDL-LPEB irradiation hybrid surface treatment. The decrease in extent of crater formation and phase transformation has enabled an improvement in corrosion resistance. The ability of the resolidified layer formed after the hybrid HPDL-LPEB irradiation to form a stable passive film shifts the pitting potential from less than 0 mV/SCE (for untreated 304 SS) to more than +800 mV/SCE, which reduced the depth of corroded pits by 75%. The hybrid HPDL-LPEB irradiation decreased non-metallic inclusions, extent of crater formation and the surface roughness, and improved the pitting corrosion and general corrosion resistance.

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.

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.

Temperature predictive model of the large pulsed electron beam (LPEB) irradiation on engineering alloys

The pulsed electron beam irradiation process is a relatively advanced technique for surface modification, including surface hardening, corrosion protection, and wear inhibition. Due to increasing demand for surface modification processes on solid metals, many experimental studies have focused on electron beam irradiation processes. In this study, a three-dimensional numerical model of the large electron beam irradiation with a Gaussian-distributed heat source was developed. To reflect the natural interactions between accelerated electrons and solid substrates, the absorptance of the electron beam was evaluated with considering electron scattering, backscattering, and transmission. Predictions of temperature distributions were validated by measuring molten depths of engineering alloys after the electron beam irradiation. The effects of absorptance on the prediction accuracy of the molten depth were also explored, and the computational results were compared based on constant and calculated absorptance versus depth. The consideration of energy absorbing mechanisms resulted in more accurate predictions of molten depths, as demonstrated by the strong agreement with experimental results.

Large Pulsed Electron Beam Welded Percolation Networks of Silver Nanowires for Transparent and Flexible Electrodes.

Mechanical properties of transparent electrodes, including flexibility, are important in flexible electronics for sustaining electrical conductivity under bending with small radius of curvature. Low contact resistance of junctions in metal nanowire percolation networks is the most important factor to produce electrodes with excellent optical, electrical and mechanical performance. Here, we report the fabrication of welded silver nanowire percolation networks using large pulsed electron beam (LPEB) irradiation as a welding process of silver nanowires (AgNWs). It results in modification of electrical and mechanical properties because of the low contact resistance at welded junctions. Consequently, the flexible and transparent AgNW electrodes fabricated by LPEB irradiation showed lower sheet resistance of 12.63 Ω sq(-1) at high transmittance of 93% (at 550 nm), and superb mechanical flexibility, compared with other AgNW electrodes prepared by thermal treatement and without any treatment. Polymer light-emitting diodes (PLEDs) using AgNWs by LPEB irradiation were fabricated to confirm that the AgNW electrode by LPEB irradiation was able to become alternative to indium tin oxide (ITO) and they showed good device performance as a maximum luminous efficiency of 7.37 cd A(-1), and excellent mechanical flexibility under bending with small radius of curvature.

Fabrication of durable hydrophobic micropatterns on stainless steel using a hybrid irradiation process

Abstract Patterns were fabricated on AISI 304 stainless steel combining the wire electric-discharge machining (WEDM) with large pulsed electron beam (LPEB) irradiation to improve the surface hydrophobicity and corrosion resistance of the alloy. The WEDM-fabricated patterns showed a Wenzel-to-Cassie transition with contact angle (CA) of 140° at a groove depth of 250 μm, which indicated hydrophobic surface. LPEB irradiation of the WEDM-fabricated patterns increased the CA (166.7°) to the Cassie state at a lower groove depth of 200 μm. The LPEB-irradiated patterns had smooth surfaces that decreased the critical angle for Wenzel-to-Cassie transition. Attenuated total reflection-infrared spectroscopy revealed that hydrophilic functional groups on the surface were absent following LPEB irradiation. LPEB irradiation modified the surface corrosion resistance of a WEDM-fabricated pattern, likely because of a lower surface energy and formation of a passive resolidified layer following irradiation.

Mechanical properties and corrosion behavior of the nitriding surface layer of Ti[sbnd]6Al[sbnd]7Nb using large pulsed electron beam (LPEB)

Large pulsed electron beam (LPEB) irradiation was used as a single surface finishing process for TiAl7Nb. Nitrogen plasma gas and cathodic apparatus have been adopted to induce nitriding effect of Ti6Al7Nb during the electron beam irradiation. The atomic concentration of nitrogen atoms at the re-solidified layer could be achieved up to ∼18% by LPEB nitriding. Nano-hardness in the re-solidified layer was improved by ∼75% following the irradiation process, as a result of a phase transformation and the formation of TiN. The re-solidified layer induced by the LPEB nitriding, consisted of TiN, TiO2, and TiOxNy, indicated significantly modified corrosion resistance showing a nobler corrosion potential, decreased corrosion current density, and improved charge transfer resistance. The increasing fraction of TiN at the re-solidified layer, induced by LPEB nitriding, was suggested as being responsible for remarkable improvement of mechanical properties and corrosion resistance, embedding uniformly noble and stable characteristics at the top surface. The corrosion-resistant surface layer with superior mechanical properties on Ti6Al7Nb has been successfully demonstrated by LPEB nitriding technique.

Hybrid deburring process assisted by a large pulsed electron beam (LPEB) for laser-fabricated patterned metal masks

The quality of pixels on displays and semiconductors is directly related to the surface quality of the patterned metal mask used. Burrs generated on the patterned metal mask can degrade the quality of pixels on microelectronic devices during the deposition process. In this study, experimental observations of abrasive deburring along with large pulsed electron beam (LPEB) irradiation were performed to evaluate the deburring effects on patterned metal masks. Numerical modeling of LPEB irradiation approximately predicted melting depths and the experimental studies revealed limitations in the size of burrs removed by LPEB irradiation. Thus a LPEB-assisted hybrid deburring process was developed to eliminate burrs of metal masks regardless of their size. The size of burrs remaining after the LPEB-assisted hybrid deburring process was reduced to approximately 7.2μm which was much less than the results of abrasive deburring alone (38.01μm). The burr size distribution was reduced by 85% and surface roughness (Ra) was decreased from 640nm to 121nm, indicating a uniform surface texture.

Influence of a large pulsed electron beam (LPEB) on the corrosion resistance of Ti−6Al−7Nb alloys

Pulsed electron-beam irradiation was used as a finishing process for Ti−6Al−7Nb titanium alloy to increase the corrosion resistance and surface hardness. The corrosion characteristics were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy to obtain Nyquist plots and log(f)–|Z| plots. The surface hardness was examined using nano-indentation with a Berkovich tip. The corrosion resistance of the irradiated surface increased, exhibiting a nobler corrosion potential, a higher polarization resistance, and a lower corrosion current density than the untreated surface. The variation in the contact angle and formation of a re-solidified passivation layer indicate a stable surface. The surface hardness increased significantly following irradiation, which was attributed to an increase in the density of dislocations and a decrease in the fraction of the pre-dominant slip plane.

Large pulsed electron beam (LPEB)-processed woven carbon fiber/ZnO nanorod/polyester resin composites

Abstract The surface modification of materials by large pulsed electron beam (LPEB) processing is an emerging eco-friendly technique that can be applied to relatively large surface areas. In this study, a polyester-based woven carbon fiber (WCF)/ZnO nanorod hybrid composite was developed using a vacuum-assisted resin transfer molding process. LPEB processing was used to modify the surface of the carbon fiber (CF) composite prior to the growth of the ZnO nanorods. The effects of this electron beam treatment on WCFs were investigated by scanning electron microscopy as a function of ZnO nanorod growth. LPEB treatment resulted in a remarkable increase in the growth of ZnO nanorods. This increase, which resulted in an increase in the electrical resistance of the samples, was further investigated by X-ray diffraction analyses. LPEB-treated samples exhibited higher impact resistance due to strong interactions among the ZnO, CF, and polyester resin.

Large pulsed electron beam surface treatment of translucent PMMA

Abstract A large pulsed electron beam (LPEB) was used to modify the surface properties of a poly(methyl methacrylate) (PMMA) sample. Translucent PMMA samples were fabricated using a conventional milling process. Then, the surface was irradiated with an energy density of 2 to 4 J/cm 2 by a large electron beam, 60 mm in size. Surface property characterization of the irradiated PMMA samples was performed using an ultraviolet–visible–near infrared (UV–vis–NIR) spectrophotometer, atomic force microscopy, a form tracer, and drop-shape analysis and compared with the non-irradiated surface. It was observed that the visible light transmission of the prepared PMMA sample was enhanced by 40%. The surface roughness of the PMMA sample after irradiation was also reduced by 30%, compared with the baseline case with no irradiation. Additionally, the water contact angle increased as the number of LPEB shots increased.

Soft x-ray generation in gases by means of a pulsed electron beam produced in a high-voltage barier discharge

A large area pulsed electron beam is produced by a high-voltage barrier discharge. We compare the properties of the x-rays generated by stopping this beam of electrons in a thin metal foil with those generated by stopping the electrons directly in various gases. The generation of x-rays was investigated in He, Ne and Ar with and without an Al foil in the discharge chamber. It appears that, for voltages of up to 15 kV used in our experiments, x-rays are produced by the ‘bremsstrahlung’ mechanism and that characteristic x-ray radiation does not play an important role. The x-ray intensity strongly depends on the parameters of the electron beam (electron energy and current density) and the stopping material properties (Z-number). The energy of the x-ray photons is comparable to the applied voltage. The highest obtained energy in the x-ray spectrum depends on the electron energy (∼10 keV in the investigated case) and the lowest energy is determined by the transmittance of the output window and the window of the detector.

Discharge and kinetics modeling in electron-beam controlled CO<inf>2</inf>laser amplifiers

The specific computational methods used to model the spatial and temporal behavior of large pulsed electron-beam controlled CO 2 laser amplifiers are presented. The interactions between the various physical processes which occur in these devices are related to the logical structure of the model, so that the key approximations can be identified. We show that, in most cases, the uniformity of the gain can be adequately described with a two-dimensional (2-D) analysis, which uses the discharge conditions present at a single snapshot time corresponding to the peak of the discharge power. We apply these techniques to model an experiment in which the nonuniformities play an important role; and, as a second example, we demonstrate that the modeling capabilities can show the consequences of design modifications in large-aperture amplifiers.