High Energy Density Beams Research Articles

Improvement of Surface Characteristic of Material by High Energy Density Beam Irradiation

Improvement of Surface Characteristic of Material by High Energy Density Beam Irradiation

Adhesive wear behavior of FeB–FeMn–C coatings produced by GTAW

Abstract In this paper, a high energy density beam of gas tungsten arc welding (GTAW) was employed to build a surface over low carbon steel with FeMn, FeB, and graphite powders. X-ray diffraction, optical microscopy, energy dispersive X-ray analysis, scanning electron microscopy, micro hardness tester, and adhesive wear tester were used for researching behavior of the composite coating which microstructure, hardness and dry-sliding wear. Many different carbides and borides, including Mn5C2, Fe3C, B8C, MnB, B4C, Fe3B, Fe7C3, FeB, and Mn2B, were found on the coated surfaces. The microstructure analysis shows that the shape of the graphite also depends on the FeMn–FeB–C content. The smallest weight loss was obtained from Sample S4 and the critical sliding distance was enhanced by adding graphite from 5 to 20 wt% at transition from oxidative to abrasive.

Progress in the Preparation and Characterization of Convex Blazed Gratings for Hyper-Spectral Imaging Spectrometer: A Review.

Convex blazed gratings, which can effectively broaden the spectral range and improve spectral resolution, have gradually evolved into a crucial optical component for lightweight and compact imaging spectroscopy instruments. Their design, processing, and testing involve multidisciplinary interdisciplinary scientific issues, and they continue to be a major area of research in imaging optics applications. This paper summarizes the effects of various grating groove shapes and structural parameters on the spectral range and diffraction efficiency of convex blazed gratings, after providing a brief introduction to the typical functions and applications of convex blazed gratings. Firstly, the latest progress in typical processing methods for convex blazed gratings is reviewed. It focuses on the current fabrication processes and reviews their capabilities in creating convex blazed gratings from three main types of technologies, namely ultra-precision machining, high-energy density beam processing, and chemically assisted fabrication processes. Secondly, the adaptability of the manufacturing process for convex blazed gratings on different scales is summarized, analyzing the adaptation of current procedures to various grating fabrication scales and their bottlenecks. Finally, the characterization methods and future feasible characterization methods for convex blazed gratings are reviewed. The development trend of efficient and precise preparation of convex blazed gratings is pointed out.

Adhesive wear behavior of gas tungsten arc welded FeB-FeMo-C coatings

Abstract In this article, a gas tungsten arc welding is used as a high energy density beam to form a surface over 0.15% carbon steel with FeB, FeMo, and graphite powders. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using optical micrography, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectrometry. Microstructural investigations reveal that FeB-reinforced coating exhibited a homogeneous microstructure that consists of dendrites and eutectic. A lot of types of carbide and borides were formed. MoB4, Fe2MoC, B8C, Mo2BC, MoB, Fe3Mo, Fe3B, B25C, Fe7C3, FeB, Mo2B5, and MoC were seen in coated surfaces. Graphite iron boride coatings obtained by the gas tungsten arc welding process improved the wear resistance of carbon steel.

A review of high energy density beam processes for welding and additive manufacturing applications

High-energy density beam processes for welding, including laser beam welding and electron beam welding, are essential processes in many industries and provide unique characteristics that are not available with other processes used for welding. More recently, these high-energy density beams have been used to great advantage for additive manufacturing. This review of the literature serves to provide an overview of the evolution of the laser and electron beam processes including the fundamental nature of the beam itself and how such a high-energy density beam has been applied for welding. The unique nature of each process regarding weld bead formation and penetration, and metallurgical considerations are covered in detail. In addition, the evolution of monitoring systems for both characterization and control of these beam processes is reviewed. Over 500 references have been cited in this comprehensive review that will allow the reader to both understand the current state-of-the-art and explore in more detail the fundamental concepts and practical applications of these processes.

Influence of heat input on microstructure, hardness and pitting corrosion of weld metal in duplex stainless steel welded by keyhole-TIG

The efficient and accurate welding technologies, including several high-energy density beam welding technologies, are generally used to weld mid-thick duplex stainless steel (DSS). However, there are still some unresolved welding problems, i.e. blowhole, excessive content of ferrite, and coarse columnar grain. Therefore, in the present paper, the keyhole gas tungsten arc (K-TIG) welding technique, a novel process, was used. The microstructural characterization, hardness and pitting corrosion of weld metal (WM) with different heat inputs were investigated in detail. The results show that weld defects in the welded joint could be effectively avoided by appropriate welding parameters. As the heat input is enhanced, Widmanstätten austenite (WA) content increases, while fine-grained intergranular austenite (IGA) content decreases. The hardness of austenite in WM is associated with solution nitrogen and dislocation proliferation caused by deformation. Besides, the PREN of ferrite in the same WM is lower than austenite. The variation of Epit in each WM could be neglected owing to the similar chemical composition. However, the corrosion rate of WM gradually increases with the enhancement of heat input. Meanwhile, the initiation and propagation of pits could be significantly affected by the precipitate Cr2N, PREN as well as Σ3 coincident site lattice (CSL) boundaries. Furthermore, fine-grained IGA could be beneficial to improve the stability and continuity of the passive film.

Challenges in path planning of high energy density beams for additive manufacturing

As there are no cutting forces in High Energy Density (HED) beams like lasers and Electron Beam (EB), their speeds are limited only by their positioning systems. On the other hand, as the entire matrix of the 3D printed part has to be addressed by the thin beam in multiple passes in multiple layers, they have to travel several kilometers in tiny motions. Therefore, the acceleration of the motion system becomes the limiting factor than velocity or precision. The authors have proposed an area-filling strategy for EB to fill the layer with optimal squares to exploit analog and hardware computing. 3D printing requires uniform intensity slanged as flat hat shape whereas the default is Gaussian. The authors have proposed an optimal algorithm that takes into account the maximum velocity and acceleration for achieving a flat hat without any compromise on productivity.

The porosity formation mechanism in the laser-welded butt joint of 8 mm thickness Ti-6Al-4V alloy: Effect of welding speed on the metallurgical pore formation

The high energy density beam welding techniques, such as laser and electron beam welding process, have been widely used in industrial applications. In this study, the butt structures of Ti-6Al-4V alloys with the thickness up to 8 mm are successfully joined by the laser welding process. The macromorphology and microstructures of the welded joints are investigated by a scanning electron microscope (SEM). The penetration increases from 5.91 mm to 9.37 mm with the decrease of welding speed from 1.2 m/min to 0.8 m/min under the condition of equal laser power. The acicular [Formula: see text] is formed in the fusion zone, resulting from high cooling rate during the process. The metallurgical porosity formation is proposed by investigating the distribution of Al and H elements around the pores. It is concluded that the pores in the weld bead are induced by aluminum vapor and hydrogen gas from the molten pool. The diameter of metallurgical pore has a tendency to increase with the decrease of welding speed.

Heterogeneous microstructure evolution in Ti-6Al-4V alloy thin-wall components deposited by plasma arc additive manufacturing

Microstructural heterogeneity was observed in titanium alloys deposited by high-energy density beam additive manufacturing (AM) technologies in the as-built condition; these heterogeneities included the presence of coarse prior-β columnar grains, non-equilibrium layer bands(LBs), and mixed microstructures. This is particulary prominent with plasma arc AM (PAM), which has a higher heat input when compared to laser beam and electron beam AM technologies. In this study, several Ti-6Al-4V layers were deposited by PAM to investigate the characteristics of the generated microstructural heterogeneity. The results show that epitaxial growth of prior β columnar grains in the same direction is inhibited by pulsed perturbation, which results in formation of columnar grains with near-equiaxed grains. Horizontal LBs could be observed after depositing six layers. The phase transformation (β → α) followed the Burgers orientation relationship, resulting in triangular stars or rhombic patterns. Precipitation of secondary α nano dispersoids occurred along{10-10} orientation. The LB region of heterogeneity was affected by thermal cycles in the β-transus and the recrystallisation temperature ranges, which leads to α lamellae of the same orientation finally forming coarse α colonies, and dispersion strengthening of the α lamellae with α nano depersoids contributes to the microhardness.

Prediction of grain structure evolution during rapid solidification of high energy density beam induced re-melting

Grain boundary migration in the presence of concentrated sources of heat is a complex process that has a considerable impact on resultant material properties. A phase field model is presented incorporating thermal gradient and curvature driving force terms to predict how a poly-crystalline network evolves due to the application of such heat sources, as grain boundaries migrate due to local boundary curvature and time-varying thermal gradients. Various thermal scenarios are investigated, in both two and three dimensions. These scenarios include both partial and full penetration laser induced melting, the application of a linearly varying time-independent thermal field, and successive melting events where regions experience multiple melting and solidification cycles. Comparisons are made between the microstructures predicted by the proposed phase field method, during the various thermal scenarios, that agree with commonly observed phenomena. Particularly interesting is the ability to explain the differences in grain morphology between the full penetration and partial penetration welds using the phase field model and associated driving force magnitudes between the two scenarios. The model predicts the restoration of grain boundary networks in regions experiencing multiple melting events, and explains the differences in grain morphology due to the local curvature and thermal gradient effects.

Development of an All‐Fiber Coherent Beam Combining System toward High Energy Pulse Fiber Lasers

SUMMARYOur present work develops an all‐fiber coherent beam combining (CBC) system to achieve a high energy pulse fiber laser beyond pulse energy limits due to nonlinear effects in rare‐earth‐doped fibers. Coherent beam combining is a power addition technology that obtains high energy density and high beam quality because it integrates multiple laser beams in a monolight wave. However, the CBC using optical fibers is technically difficult because the optical phases and polarization in optical fibers fluctuate due to disturbances. Therefore, we developed a novel all‐fiber CBC system that can precisely control optical path lengths and automatically compensate polarization changes. When the system combined four laser pulses, it achieved a beam‐combining efficiency of 96.6% that was about four times as high as a pulse energy before combining. In addition, the system obtained 97.1% beam‐combining efficiency of CBC using femtosecond pulses that have very low coherences by minimizing the optical path‐length differences between combined two pulses. Moreover, the system successfully regulated the beam‐combining‐efficiency changes to less than 2.0 percentage points in full width by suppressing optical path‐length fluctuations and tracking‐control of the optical phases.

Ion beam induced luminescence spectra of lithium fluoride at high-and low-temperature

A new ion beam induced luminescence (IBIL) measuring setup, equipped with a custom-made heating/cooling sample stage (the attainable temperature ranges from 80 K to 900 K), has been established on the GIC4117 tandem accelerator in Beijing Normal University. As the yield of back scattering ions is proportional to the beam flux, an Au-Si surface barrier detector is employed to count the back scattering ions synchronously with collecting the IBIL spectra under the multi-channel scaler (MCS) mode of the multichannel analyzer, making it possible to online monitor the beam current. Then, the yield of back scattering ions is used to correct the intensity of the IBIL spectrum and calculate the ion fluence, for eliminating the influence of the beam current fluctuation. IBIL spectra of pure lithium fluoride (LiF) at different temperatures (100, 200, 290, 450, 550 K) under the 2 MeV H+ irradiation are acquired and the significant influence of temperature on luminescence centers is observed. The emission bands relating to exciton recombination (296 and 340 nm) and impurities (400 nm) are more prominent at low temperatures and present quite lower intensities at high temperatures. Moreover, these luminescent intensities decay with ion fluence increase obviously at high temperatures after initially increasing in the early period of irradiation. The initial increase of the disturbed exciton peak at 296 nm can be attributed to the strained bonds produced by nuclear elastic scattering at a low fluence, which was not observed in previous IBIL measurements under high ionization energy density or high ion beam flux. This observed increase indicates that the emission feature may also originate from the emitting centers relating to point defects, not just from exciton transition near lattice or impurities. The luminescent intensities of F2 color centers (peaked at 670 nm) are dominant at all temperatures, while the luminescent intensities of F3+ color centers (peaked at 540 nm) are not obvious at low temperatures and the luminescent intensities of F3-/F2+ color centers (peaked at 880 nm) are weak at high temperatures. The luminescent intensities of these F-type centers reach saturated values at lower fluences at high temperatures. The different evolution behaviors under different temperatures can be due to the influence of temperature on the vacancy migration rate and the non-radiative recombination. In addition, the surface charge accumulation may lead to the luminescent intensities of color centers reaching saturated values at higher fluences, compared with the previous IBIL measurements of LiF. The self-absorption effect would reduce the intensities of F3+ color centers because of the absorption of F-type centers at low temperatures, while the effect is weak at high temperatures due to the degradation of F-type centers.

Micro-Plasma Transferred Arc Additive Manufacturing for Die and Mold Surface Remanufacturing

Micro-plasma transferred arc (µPTA) additive manufacturing is one of the newest options for remanufacturing of dies and molds surfaces in the near-millimeter range leading to extended usage of the same. We deployed an automatic micro-plasma deposition setup to deposit a wire of 300 µm of AISI P20 tool steel on the substrate of same material for the potential application in remanufacturing of the die and mold surface. Our present research effort is to establish µPTA additive manufacturing as a viable economical and cleaner methodology for potential industrial applications. We undertook the optimization of single weld bead geometry as the first step in our present study. Bead-on-plate trials were conducted to deposit single bead geometry at various processing parameters. The bead geometry (shape and size) and dilution were measured and the parametric dependence was derived. A set of parameters leading to reproducible regular and smooth single bead geometry were identified and used to prepare a thin wall for mechanical testing. The deposits were subjected to material characterization such as microscopic studies, micro-hardness measurements and tensile testing. The process was compared qualitatively with other deposition processes involving high-energy density beams and was found to be advantageous in terms of low initial and running costs with comparable properties. The outcome of the study confirmed the process capability of µPTA deposition leading to deployment of cost-effective and environmentally friendlier technology for die and mold remanufacturing.

Joining of Inconel 718 and 316 Stainless Steel using electron beam melting additive manufacturing technology

Joining of dissimilar metals using high energy-density beams such as lasers and electron beams offer several advantages including precision, narrow fusion zones, and narrow heat affected zones (HAZ) that consequently result in reduced part distortion when compared to traditional joining processes. When high energy-density beams are combined with the design freedom offered by additive manufacturing (AM), or a layer-by-layer part fabrication process, it becomes possible to manufacture complex multi-material parts with improved joint characteristics resulting from controlled process parameters. Complex multi-material parts can be achieved that have tremendous impact on applications ranging from nuclear power plant components to repair applications. This research explores the feasibility of joining Inconel 718 with 316L Stainless Steel, and vice versa, by utilizing electron beam melting (EBM) additive manufacturing, a class of powder bed fusion technology. The use of this process can help avoid the use of filler materials, provides an evacuated processing environment resulting in limited contamination of oxides and nitrides, and can provide a high quality metallurgical joint while minimizing the thermal damage to surrounding material. Multi-material components were fabricated and the joint interfaces were characterized. Assessments of the interfaces revealed minimized thermal effects from the process and finer weld joints.

Welding of Acryalics Using Laser Beam:An Experimental Investigation

Laser beam welding (LBW) uses high energy density beam making it suitable for welding of wide category of materials. As energy density around the focal point of laser beams is quite high, this technique is being increasingly used in the fabrication industry. Since laser beams follow the principle of optics, it can be easily regulated by selecting appropriate lenses. In this paper, a report on the experimental work involving laser beam welding (LBW) is presented where lap joints of two acryalic (polycarbonate) flats-one opaque and the other transparent, are tried to make. Laser beam passes through the transparent piece of plastic flat, and is focused on to the opaque flat around the interface region. Laser beam gets absorbed in the opaque flat in the interface region and generates heat energy causing local melting, and subsequent welding of both the flats. This method is named as through transmission laser welding. The bonding between the two components is likely to occur by interpenetration of molecular chains in the area that is promoted by fluidity of acrylic during welding. Process parameters such as clamping pressure and current are varied at some selected scanning speeds to explore the appropriate condition to obtain sound, strong weld joint within the experimental domain. The laser has a repetitive operating current less than 60 A with pulse frequency of 0.25-10 kHz. The used 30 W laser system is having spectral width of 1.69 nm, beam divergence of less than 0.20 N.A. and beam diameter of 800 urn with a wavelength of 809.40 μn. Scanning speed of 240,280,320 and 360 mm/min, current flow of 25,28,31 and 34 A, and clamping pressure of 20, 30,40 and 50 Kg/cm 2 are chosen in this work. Sound welded joint between transparent and opaque acryalic components with high weld strength above 8 MPa is obtained under scanning speeds of 280 and 360 mm/min and 20 Kg/cm 2 clamping pressure with weld current setting of 28, 31 and 34 A. Suitable heat input to the weld interface may have resulted in this observation. Therefore, these conditions may be recommended to apply to obtain large weld strength.

Directly Manufacturing Table Tennis Mould by Hybrid Plasma Deposition & Milling

A table tennis mould with good performance of dimensional precision and fine surface roughness was directly manufactured by HPDM (Hybrid Plasma Deposition & Milling), which synthesizes plasma deposition as an additive technology, and milling as a subtractive technique during the processing. Compared with the existing RP methods using high energy density beams, the HPDM method solved the key problems of insufficient dimensional precision and surface quality caused by the step effect, and puts forward a new access to directly manufacture the metal parts and mould with short-process and high quality.

Focusing Dynamics of High-Energy Density, Laser-Driven Ion Beams

The dynamics of the focusing of laser-driven ion beams produced from concave solid targets was studied. Most of the ion beam energy is observed to converge at the center of the cylindrical targets with a spot diameter of 30 μm, which can be very beneficial for applications requiring high beam energy densities. Also, unbalanced laser irradiation does not compromise the focusability of the beam. However, significant filamentation occurs during the focusing, potentially limiting the localization of the energy deposition region by these beams at focus. These effects could impact the applicability of such high-energy density beams for applications, e.g., in proton-driven fast ignition.

Investigation on Mechanical Properties of Pulsed Nd:YAG Laser Welding on AISI 304 Stainless Steel to AISI 1008 Steel

Product with low cost, lightweight and enhanced mechanical properties were the main reasons welding dissimilar materials thrived by most of the industries. The laser welding technique which has high-energy density beam was found suitable of carrying this task. This paper attempts to investigate welding of AISI 304 stainless steel to AISI 1008 steel through Nd:YAG pulse laser method. The main objective of this study was to find out the weldability of these materials and investigate the mechanical properties of the welded butt joints. Peak power, pulse duration and weld speed combinations were carefully selected with the aims of producing weld with a good tensile strength, minimum heat affected zone (HAZ) and acceptable welding profile. Response surface methodology (RSM) approach was adopted as statistical design technique for tensile strength optimization. Statistical based mathematical model was developed to describe effects of each process parameters on the weld tensile strength and for response prediction within the parameter ranges. The microstructure of the weld and heat affected zones were observed via optical microscope. The results indicate the developed model can predict the response within ±9% of error from the actual values.

High-energy density beams and plasmas for micro- and nano-texturing of surfaces by rapid melting and solidification

Several advances in materials research have been made due to the wide array of tools currently available for the processing of materials: plasmas, electron beams, ion beams and lasers. The area of material science is fortunate to have seen the development of these tools over the years, be it for new bulk materials, coatings or for surface modification. Several applications have benefited and many more will in the future as the properties of the materials are altered on a micro/nanoscale. Currently, several techniques exist to modify the physical, chemical and biological properties of the material surface; however, this review limits itself to surface modification applications using the rapid thermal processing (RTP) technique. First, a brief overview of the existing surface modification methods using the principles of RTP is reviewed, and then a novel method to create micro/nanostructures on the surface using pulsed plasma exposure of materials is presented.

Promotion of Adhesive and Wear Performances of Chromium Coating with Plasma Non-Transferred Arc Treatment

Plasma arc, a kind of high energy density beam, is proposed as one kind of surface treatments in this paper to improve the adhesive properties of the chromium coatings to the steel substrate. Scratch tests are used to obtain the critical load (Lc) of the coatings. The wear behaviors are evaluated by a reciprocating ball-on-flat wear machine and the wear tracks of the coating were characterized by scanning electronic microscope (SEM). Results show that plasma arc treatment could promote the adhesive and the wear performances of the chromium coatings. Optimal value of Lc and the wear resistance of the treated coatings could be obtained when the average output energy density of the plasma arc (E) grow to 1.05×105J/m2. The comparative study indicates that the promotion of the adhesion could be attributed to the formation of the inter-diffused alloyed layer and the improved hardness distribution. This promotion then contributes to the improvement of the wear performance, which makes up, even exceeds the loss of it caused by the drop of the coatings hardness.