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Effects of Substrate Preheating Temperatures on the Microstructure, Properties, and Residual Stress of 12CrNi2 Prepared by Laser Cladding Deposition Technique
摘要： The 12CrNi2 alloy steel powder studied in the present paper is mainly used to manufacture camshafts for nuclear power emergency diesel engines. Laser cladding deposition is of great signi?cance for the manufacture of nuclear power emergency diesel camshafts, which has the advantages of reducing material cost and shortening the manufacturing cycle. However, due to the extremely uneven heating of the components during the deposition process, a complex residual stress ?eld occurs, resulting in crack defects and residual deformation of the components. In the present paper, 12CrNi2 bulk specimens were prepared on the Q460E high-strength structural steel substrate at different preheating temperatures by laser cladding deposition technique, and a ?nite element residual stress analysis model was established to investigate the effects of different preheating temperatures on the microstructure, properties, and residual stress of the specimens. The results of the experiments and ?nite element simulations show that with the increase of preheating temperature, the content of martensite/bainite in the deposited layer decreases, and the ferrite content increases. The proper preheating temperature (150 ?C) has good mechanical properties. The residual stress on the surface of each specimen decreases with the increase of the preheating temperature. The longitudinal stress is greater at the rear-end deposition part, and the lateral residual stress is greater on both sides along the scanning direction.
关键词： substrate preheating,12CrNi2 alloy steel powder,residual stress,laser cladding deposition,microstructure and properties
更新于2025-11-28 14:24:20
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Development of an Intra-Layer Adaptive Toolpath Generation Control Procedure in the Laser Metal Wire Deposition Process
摘要： Recently developed concentric laser metal wire deposition (LMWD) heads allow metal addition processes which are independent of the deposition direction, thus enabling complex paths to be generated. The sensitivity of the process to height deviations has experimentally been observed to be greater with this type of head than with powder ones, therefore requiring more precise and local process control algorithms to be implemented. This work developed a methodology for measuring the part, layer by layer, using a 3D scanner based on structured laser light. Height corrections were applied to the mean and intra-layer height deviations by recalculating the deposition trajectories of the next layer to be deposited. Local height deviations were adjusted by varying the scanning speed, thus increasing the feed rate in the lower areas and decreasing it in the higher ones. Defects generated in the purpose, with height differences within the layer, were successfully corrected. A flat layer was re-established through the application of the control strategy. The internal integrity of the parts due to the scanning speed variation was analyzed, resulting in fully dense parts. The structured light measurement and height correction systems are found to be an affordable and time-efficient solution that can be integrated into an LMWD environment, thereby improving the process robustness.
关键词： cladding,coaxial wire feed,metal wire,additive manufacturing,monitoring,laser deposition,structured light scanning,height control
更新于2025-11-28 14:24:20
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Energy efficiency evaluation of metal laser direct deposition based on process characteristics and empirical modeling
摘要： Metal laser direct deposition (MLDD) is a typical process in additive manufacturing (AM), which permits the build of complex and fully dense metallic parts by using laser to melt the metal powder layer by layer. However, the process is characterized by high energy consumption and low energy efficiency. This paper established an empirical model to characterize the relationship between process parameters and energy efficiency for MLDD based on the essence of thermodynamics physical energy conversion. Additionally, a recognition method of cross-sectional profile of the deposited layer was achieved by adding tungsten carbide (WC) powder, which greatly improved the measurement reliability. Taguchi experiment and regression identification method were applied, and the relative error of the model was less than 10%. The results show that laser power has significant influence on the process energy efficiency of MLDD. The energy efficiency of single-track multi-layer stacking (SMS) process and multi-track single-layer lapping (MSL) process increased by 5.7% and 50.3%, respectively, under the optimal process parameter condition. The proposed model can be used effectively for the energy efficiency evaluation and offer the potential for improving the sustainability of MLDD.
关键词： Energy efficiency,Metal laser direct deposition (MLDD),Cross-sectional profile,Taguchi experiment
更新于2025-11-28 14:24:20
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Influence of processing parameters on the microstructure and tensile property of 85 W-15Ni produced by laser direct deposition
摘要： The plate-like shape 85W-15Ni parts were produced by laser direct deposition technology with different processing parameters (laser power and scanning speed). The influence of processing parameters and their corresponding laser energy density on the microstructural characterization, phase composition and tensile property of 85W-15Ni samples was investigated. The results show that the relative density of samples increased with the laser energy density and the densification trend started to slow as the laser energy density reached 380-400 J/mm3, though the highest density value was obtained with laser energy of 425 J/mm3. With the increase of laser energy density, more disorder and fine W dendrites existed at the bonding region between deposition layers and more W-W grain boundaries formed at the central region of the layer. The 85W-15Ni samples produced with different processing parameters consisted of W and γ-Ni phase. To improve the tensile property, it is necessary to increase the laser energy density to obtain denser structure and reduce the residual pores or gaps. However, the excessive laser energy density resulted in the formation of more W-W grain boundaries that were detrimental to the tensile property. The best tensile properties were obtained at the laser energy density of 395 J/mm3.
关键词： 85W-15Ni,Laser direct deposition,Tensile property,Laser energy density,microstructural characterization
更新于2025-11-28 14:24:20
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Influence of Technological Parameters of Direct Laser Deposition Process on the Structure and Properties of Deposited Products from Alloy Ti-6Al-4V
摘要： The technology of direct laser deposition is the most promising for using in various industries. One of the most interesting areas for using this technology is an aviation industry. Due to their unique properties, titanium alloys are widely used in the aircraft industry for gas turbine engine components. In this paper, the effect of DLD process parameters on defect formation and structure is considered. The influence of energy density on the mechanical properties of parts is determined.
关键词： Direct Laser Deposition,additive manufacturing,mechanical properties,Titanium alloys
更新于2025-11-28 14:24:20
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Epitaxy and new stray grain formation mechanism during epitaxial laser melting deposition of Inconel 718 on directionally solidified nickel-based superalloys
摘要： The epitaxy behavior and stray grains (SGs) formation in the deposit during epitaxial laser melting deposition (E-LMD) of directionally solidified (DS) superalloys were investigated. Columnar dendritic structures were obtained by epitaxial solidification on the DS substrate. The deposit also remained the orientation of the substrate. The SGs at the fusion interface, which were hardly eliminated, were attributed to different SGs formation mechanisms. The SGs were divided into GB-SGs and MC-SGs by the distribution characteristics. The GB-SGs at the low-angle and high-angle grain boundaries with a new mechanism of dynamic recrystallization induced by accumulation of thermal strain and stress under repeated spatially variable heating and cooling. The MC-SGs around the carbides were related to the misoriented cellular crystal formation caused by the varied shape of the solid-liquid interface. The columnar to equiaxed transition (CET) was another mechanism of MC-SGs formation.
关键词： Stray grain,Nickel superalloys,Laser metal deposition,Recrystallization,Dynamic,Epitaxy,Microstructure
更新于2025-11-28 14:24:20
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Effects of phase transition temperature and preheating on residual stress in multi-pass & multi-layer laser metal deposition
摘要： To investigate the influences of phase transition temperature and preheating on the residual stress of multi-layer and multi-pass laser metal deposition (LMD), the multi-layer and multi-pass LMD, with and without preheating, were performed using five kinds of alloy with different phase transition features, and their residual stresses were measured using the hole drilling method. A finite-element (FE) model incorporating the phase transition was developed based on experimentally obtained physical property data. The results demonstrated that the low-temperature solid phase transition has a tensile stress relaxation effect, which leads to the formation of a compressive stress area. This relaxation effect was observed to decrease with the increase of the phase transition temperature. The high-temperature solid phase transition has no significant tensile stress relaxation effect during the multi-layer and multi-pass LMD process, which is different from the single track LMD. when the solid phase transition temperature is low, the preheating can improve the uniformity of the stress field only to a certain extent. However, when the preheating increases the lowest temperature of the thermal cycle and makes it higher than the starting point temperature of the solid phase transition, the tensile stress relaxation effect of the solid phase transition can be brought into full play.
关键词： Finite element analysis,Preheating,phase transition temperature,Residual stress,Laser metal deposition
更新于2025-11-28 14:24:20
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Microstructural Characteristics of Laser Metal Deposited Magnesium Alloy AZ31
摘要： Up to now, only a limited amount of metallic materials is investigated for laser additive manufacturing (LAM). However, the demand to widen the application possibilities by enlarging the range of materials for LAM is growing fast. By now, titanium and aluminium alloys are in the focus of research. In contrast, magnesium alloys are rarely used in the field of additive manufacturing, although they possess a low density in combination with a high specific strength. Currently, magnesium structures are mainly produced by casting but during the last years, the use of wrought alloys also increased. A reason for the rare use of magnesium alloys for LAM technologies might be the high flammability of magnesium powders. This difficulty can be avoided by using magnesium wire for laser metal deposition (LMD). In the present study, the microstructural characteristics of a LMD processed AZ31 magnesium alloy are investigated. For this purpose, optical microscopy and scanning electron microscopy were used. With the help of EDX and EBSD analysis, a change of the chemical composition and micro texture with structure height was identified. The relationship of microstructure and local mechanical properties was investigated with the help of Vickers micro hardness testing. Based on the obtained results it can be concluded that the microstructural characteristics of laser additive manufactured magnesium alloys differ from those of titanium and aluminium alloys. Thus, a wider application spectrum of LMD and magnesium alloys can be opened up.
关键词： laser metal deposition,local mechanical properties,microstructure,magnesium alloy,wire,microtexture
更新于2025-11-28 14:24:20
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Ultrasensitive tantalum oxide nano-coated long-period gratings for detection of various biological targets
摘要： In this work we discussed a label-free biosensing application of long-period gratings (LPGs) optimized in refractive index (RI) sensitivity by deposition of thin tantalum oxide (TaOx) overlays. Comparing to other thin film and materials already applied for maximizing the RI sensitivity, TaOx offers good chemical and mechanical stability during its surface functionalization and other biosensing experiments. It was shown theoretically and experimentally that when RI of the overlay is as high as 2 in IR spectral range, for obtaining LPGs ultrasensitive to RI, the overlay’s thickness must be determined with subnanometer precision. In this experiment the TaOx overlays were deposited using Atomic Layer Deposition method that allowed for achieving overlays with exceptionally well-defined thickness and optical properties. The TaOx nano-coated LPGs show RI sensitivity determined for a single resonance exceeding 11,500 nm/RIU in RI range nD=1.335-1.345 RIU, as expected for label-free biosensing applications. Capability for detection of various in size biological targets, i.e., proteins (avidin) and bacteria (Escherichia coli), with TaOx-coated LPGs was verified using biotin and bacteriophage adhesin as recognition elements, respectively. It has been shown that functionalization process, as well as type of recognition elements and target analyte must be taken into consideration when the LPG sensitivity is optimized. In this work optimized approach made possible detection of small in size biological targets such as proteins with sensitivity reaching 10.21 nm/log(ng/ml).
关键词： protein detection,label-free biosensing,optical fiber sensor,tantalum oxide,bacteria detection,long-period grating,atomic layer deposition
更新于2025-11-28 14:23:57
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Dual-Functional Long-Term Plasticity Emulated in IGZO-Based Photoelectric Neuromorphic Transistors
摘要： Indium–gallium–zinc-oxide (IGZO) photoelectric neuromorphic transistors with low-temperature atomic layer deposited Al2O3 gate dielectrics are fabricated. Dual-functional long-term plasticity, including long-term depression (LTD) and long-term potentiation (LTP), is emulated. The emulation of LTD is achieved by applying high-electrical pulse trains on the gate electrode. The LTP emulation is realized by applying light pulse trains on the IGZO channel layer. The operation mechanisms of the LTD and the LTP are discussed based on the electron/hole trapping in the Al2O3 gate dielectrics and the persistent photoconductivity of the IGZO channel layer.
关键词： Neuromorphic transistors,long-term plasticity,atomic layer deposition
更新于2025-11-25 10:30:42