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Study for Combined Wire + Powder Laser Metal Deposition of H11 and Niobium
摘要： Laser additive manufacturing (LAM) has been proved to be a successful technique to fabricate metallic components for a number of industries; for instance, die & mold, forging and cutting tools, and aerospace. It is, however, facing multitude obstacles due to lack of maturity in terms of process knowledge, design, and qualification. This paper deals with parameters’ study and optimization of combined hot-work tool steel wire (H11) and niobium powder (Nb) deposition by laser. The process is closely analysed and compared with as well as without using Nb powder. Especially, the importance of Nb in order to refine the microstructure is discussed while taking into account the microstructure-property relationships of H11.
关键词： Laser additive manufacturing,Niobium (Nb),Hot-work tool steel,Laser metal deposition,H11
更新于2025-09-16 10:30:52
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Process-Structure-Properties-Performance Modeling for Selective Laser Melting
摘要： Selective laser melting (SLM) is a promising manufacturing technique where the part design, from performance and properties process control and alloying, can be accelerated with integrated computational materials engineering (ICME). This paper demonstrates a process-structure-properties-performance modeling framework for SLM. For powder-bed scale melt pool modeling, we present a diffuse-interface multiphase computational fluid dynamics model which couples Navier–Stokes, Cahn–Hilliard, and heat-transfer equations. A computationally efficient large-scale heat-transfer model is used to describe the temperature evolution in larger volumes. Phase field modeling is used to demonstrate how epitaxial growth of Ti-6-4 can be interrupted with inoculants to obtain an equiaxed polycrystalline structure. These structures are enriched with a synthetic lath martensite substructure, and their micromechanical response are investigated with a crystal plasticity model. The fatigue performance of these structures are analyzed, with spherical porelike defects and high-aspect-ratio cracklike defects incorporated, and a cycle-amplitude fatigue graph is produced to quantify the fatigue behavior of the structures. The simulated fatigue life presents trends consistent with the literature in terms of high cycle and low cycle fatigue, and the role of defects in dominating the respective performance of the produced SLM structures. The proposed ICME workflow emphasizes the possibilities arising from the vast design space exploitable with respect to manufacturing systems, powders, respective alloy chemistries, and microstructures. By digitalizing the whole workflow and enabling a thorough and detailed virtual evaluation of the causal relationships, the promise of product-targeted materials and solutions for metal additive manufacturing becomes closer to practical engineering application.
关键词： heat-transfer modeling,additive manufacturing,phase field modeling,integrated computational materials engineering,crystal plasticity,selective laser melting,micromechanical modeling
更新于2025-09-16 10:30:52
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Study on Effect of Post Processing on Direct Metal LASER Sintered 420 Stainless steel Infiltrated with Bronze
摘要： Additive manufacturing (AM) of metals is increasing its potential applications in the areas of aerospace, automobile, defense and medical with the processing capability from light to heavy metals, but still low density of the finished products which causes discrimination to functional properties and thus reducing AM process real time efficiency. Current research focus on improving the functional properties of 420 stainless steel specimens which are fabricated by Direct Metal LASER Sintering (DMLS) process and infiltrated with bronze for improving the density. Also post processing i.e. annealing, deep cryogenic treatment and tempering was performed. By studying the mechanical properties like tensile strength, hardness, wear of material of specimens in as fabricated and post processed condition it was observed that post processing treatment will favours in enhancing the functional properties. Also results are compared with SEM and optical microscopy images in order to determine microstructural changes.
关键词： deep cryogenic treatment,Infiltration with bronze,Additive manufacturing,420 stainless steel,annealing,tempering
更新于2025-09-16 10:30:52
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Slotted Hemispherical Resonators for 3-D Printed Waveguide Filters With Extended Spurious-Free Stopbands
摘要： This paper presents a comprehensive study on a new family of slotted hemispherical resonators and their applications in waveguide bandpass filters (BPFs) to extend the spurious-free stopbands. The proposed scheme focuses on suppressing unwanted spurious modes in the air-filled hemispherical resonators by adding functional slots to the metallic cavity shells. The spurious TM2m1 and TE101 modes in the hemispherical resonators are effectively suppressed by interrupting the surface current with slots, without significantly degrading the unloaded quality factor of the fundamental TM101 mode. Resonant modes in the slotted hemispherical resonators are analyzed. Design, fabrication, and measurement of X-band proof-of-concept waveguide BPFs based on slotted hemispherical resonators are expounded. Each filter is monolithically prototyped by employing metallic additive manufacturing technology. The filters demonstrate good passband performance—average insertion loss: 0.6–1.1 dB, frequency shift: 0.9%–1%, and return loss: >20 dB, and more significantly extended stopbands with spurious-free frequency ratios of >1.8:1 and stopband rejections over 36 dB.
关键词： spurious suppression,slotted hemispherical resonator,waveguide filter,direct metal laser sintering,spurious-free stopband,Additive manufacturing
更新于2025-09-16 10:30:52
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Austenitic Stainless Steel Powders with Increased Nitrogen Content for Laser Additive Manufacturing
摘要： Nitrogen is used as an alloying element, substituting the expensive and allergenic element nickel, in austenitic stainless steels to improve their mechanical properties and corrosion resistance. The development of austenitic stainless steel powders with increased nitrogen content for laser additive manufacturing has recently received great interest. To increase nitrogen content in the austenitic steel powders (for example AISI 316L), two measures are taken in this study: (1) melting the steel under a nitrogen atmosphere, and (2) adding manganese to increase the solubility of nitrogen in the steel. The steel melt is then atomized by means of gas atomization (with either nitrogen or argon). The resulting powders are examined and characterized with regard to nitrogen content, particle size distribution, particle shape, microstructure, and ?owability. It shows that about 0.2–0.3 mass % nitrogen can be added to the austenitic stainless steel 316L by adding manganese and melting the steel under nitrogen atmosphere. The particles are spherical in shape and very few satellite particles are observed. The steel powders show good ?owability and packing density, therefore they can be successfully processed by means of laser powder bed fusion (L-PBF).
关键词： nitrogen alloying,powder production,austenitic stainless steel,gas atomization,laser additive manufacturing
更新于2025-09-16 10:30:52
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[IEEE 2019 17th International Conference on ICT and Knowledge Engineering (ICT&KE) - Bangkok, Thailand (2019.11.20-2019.11.22)] 2019 17th International Conference on ICT and Knowledge Engineering (ICT&KE) - Provision and Visualization of Solar Radiation Data for Energy Management System
摘要： This paper reports the design, fabrication, and characterization of arrays of miniaturized, internally fed, polymer electrospray emitters fabricated with stereolithography. The freeform additive manufacturing process used to make the devices has associated two orders of magnitude reduction in the fabrication cost per device and fabrication time (from thousands of dollars to tens of dollars, and from months to hours, respectively) and a two orders of magnitude reduction in the cost of the manufacturing infrastructure (from millions of dollars to tens of thousands of dollars) compared with a silicon MEMS multiplexed electrospray source. The 3-D printed devices include features not easily attainable with other microfabrication methods, e.g., tapered channels and threaded holes. Through the optimization of the fabrication process 10-mm tall, isolated, straight, solid columns with diameter as small as 300 μm, and 12-mm long, straight tubes with inner diameter as small as 400 μm and wall thickness as small as 150 μm were demonstrated. Arrays with as many as 236 internally fed electrospray emitters (236 emitters in 1 cm2) were made, i.e., a twofold increase in emitter density and a sixfold increase in array size compared with the best reported values from multiplexed, internally fed, electrospray sources made of polymer. The characterization of devices with a different array size suggests a uniform emitter operation.
关键词： electrospray,Additive manufacturing of MEMS,stereolithography,multiplexed liquid ionizers
更新于2025-09-16 10:30:52
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Processing of X65MoCrWV3a??2 Cold Work Tool Steel by Laser Powder Bed Fusion
摘要： Laser powder bed fusion (L-PBF) of forming tools has become of major interest in the tooling industry because of the high geometrical flexibility of this process. During L-PBF, a metallic powder bed is melted selectively by a laser beam, enabling the layer-wise manufacturing of parts from 3D computer-aided design data. The process is characterized by a locally and temporally unsteady heat flow in the solidified part and in the melt pool, causing nonequilibrium solidification and phase transformations. In addition, rapid heating and cooling occur, promoting the formation of microstructural defects, cold cracks, and distortion. Because of the high tendency to form cold cracks, processing of martensitic tool steels is still a challenging task. Tool steel X65MoCrWV3-2 is processed by L-PBF and the resulting microstructure and the associated local properties are investigated by microhardness measurements, nanoindentation, and scanning electron microscopy. It is gathered from the investigations that regions of different microstructures and mechanical properties on both micro- and macroscale are present in the L-PBF-densified steel. The different microstructures and properties are the result of the alternating heat insert at different temperature regimes, forming heat-affected zones in which the tempering processes are triggered and strongly varying properties are generated.
关键词： additive manufacturing,martensite,microstructure formation,laser powder bed fusion,tool steels
更新于2025-09-16 10:30:52
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Electropolishing of Laser Powder Bed-Fused IN625 Components in an Ionic Electrolyte
摘要： This work presents the first practical application of ionic electrolytes for electropolishing of nickel-based superalloys. It contains the results of an experiment-driven optimization of the applied potential and electrolyte temperature during electropolishing of laser powder bed-fused IN625 components containing surfaces oriented to the building platform under angles varying from 0 to 135°. For comparative purposes, the roughness profilometry and confocal microscopy techniques were used to characterize the surface finish topographies and the material removal rates of IN625 components subjected to electropolishing in ionic and acidic (reference) electrolytes. After 4 h of electropolishing in both electrolytes, a roughness of Ra ≤ 6.3 μm (ISO N9 grade number of roughness) was obtained for all the build orientations. To elaborate, both electrolytes manifested identical roughness evolutions with time on the 45°(75% Ra reduction) and 90°-oriented (65% Ra reduction) surfaces. Although the roughness reduction on the 135°-oriented surface in the ionic electrolyte was 17% less than in the acidic electrolyte, the former provided a more uniform roughness profile on the 0°-oriented surface (30% Ra reduction) and 44% higher current efficiency than the acidic electrolyte. This work proves that ionic electrolytes constitute a greener alternative to industrial acidic mixtures for electropolishing of three-dimensional (3D)-printed parts from nickel-based superalloys.
关键词： ionic electrolyte,build orientation,surface finish,additive manufacturing,electropolishing,Inconel625
更新于2025-09-16 10:30:52
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Laser Cladding of Heat-Resistant Iron Based Alloy
摘要： The paper presents the results of the composition, structure and mechanical characteristics of heat-resistant iron based alloy samples produced by laser cladding. The samples were manufactured using secondary raw material (chips), which were converted into powder by plasma spheroidization. The crystalline transformations for the as-processed as well as after several heat treatment conditions were analyzed. Phase, chemical composition and mechanical characteristics were investigated.
关键词： mechanical properties,additive manufacturing,heat-resistant iron based alloy,microstructure,laser cladding
更新于2025-09-16 10:30:52
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The Effect of Laser Power on the Microstructure of the Nb-Si Based <i>In Situ</i> Composite, Fabricated by Laser Metal Deposition
摘要： The Nb-Si in-situ composite samples were fabricated by laser metal deposition additive manufacturing technology from mechanically alloyed powders in vario-planetary ball mill. A laser metal of samples was carried out at various laser powers: 500 W, 1000 W, 1400 W. The microstructure of a sample grown at a laser power of 500 W consists of a solid solution of Nb, Nb3Si, and dendritic chains of Ti. When the laser power is increased to 1000 W, the volume fraction of silicides increases, the structural heterogeneity decreases. With further increase in laser power to 1400 W, Ti dissolves in Nb, dendritic chains disappear, Nb5Si3 silicide stabilizes.
关键词： Additive manufacturing,Nb-Si based alloy,Direct energy deposition
更新于2025-09-16 10:30:52