Bibliographies: 'Direct Metal Laser Sintering' – Grafiati (2024)

Abstract:

This paper focuses on the improvement of ultrasonic defectoscopy used for machine elements produced by direct laser metal sintering. The direct laser metal sintering process introduces the mixed metal powder and performs its subsequent laser consolidation in a single production step. Mechanical elements manufactured by laser sintering often contain many hollow cells due to weight reduction. The popular pulse echo defectoscopy method employing very high frequencies of several GHz is not successful on these samples. The aim of this paper is to present quadraphonic transmission ultrasound defectoscopy which uses low range frequencies of few tens of kHz. Therefore, the advantage of this method is that it enables defectoscopy for honeycombed materials manufactured by direct laser sintering. This paper presents the results of testing performed on AlSi12 sample.

Abstract:

The direct metal laser sintering process was applied to produce density gradient materials of stainless steel 316L. In order to understand the mechanism of forming porous structure, the influence of laser power, scan rate and scan pitch on the porosity were investigated by measuring density of produced samples and observing cross-sectional microstructures. Laser power greatly affected to the porosity by forming clusters of melted metal powders. It was found that the size change of clusters plays a role in forming porous structure. Eventually, three dimensional sample owing density gradient structures was manufactured.

Abstract:

AbstractManufacturing is crucial to creation of wealth and provision of quality of life. Manufacturing covers numerous aspects from systems design and organization, technology and logistics, operational planning and control. The study of manufacturing technology is usually classified into conventional and non-conventional processes. As it is well known, the term "rapid prototyping" refers to a number of different but related technologies that can be used for building very complex physical models and prototype parts directly from 3D CAD model. Among these technologies are selective laser sintering (SLS) and direct metal laser sintering (DMLS). RP technologies can use wide range of materials which gives possibility for their application in different fields. RP has primary been developed for manufacturing industry in order to speed up the development of new products (prototypes, concept models, form, fit, and function testing, tooling patterns, final products - direct parts). Sintering is a term in the field of powder metallurgy and describes a process which takes place under a certain pressure and temperature over a period of time. During sintering particles of a powder material are bound together in a mold to a solid part. In selective laser sintering the crucial elements pressure and time are obsolete and the powder particles are only heated for a short period of time. SLS uses the fact that every physical system tends to achieve a condition of minimum energy. In the case of powder the partially melted particles aim to minimize their in comparison to a solid block of material enormous surface area through fusing their outer skins. Like all generative manufacturing processes laser sintering gains the geometrical information out of a 3D CAD model. This model is subdivided into slices or layers of a certain layer thickness. Following this is a revolving process which consists of three basic process steps: recoating, exposure, and lowering of the build platform until the part is finished completely.

Abstract:

The direct laser sintering process is currently being used to manufacture metallic parts for prototyping and tooling directly. This paper reports on the direct laser sintering of Fe—Cu metal powder using a 200 W CO2 laser. The effects of the ratio of Fe to Cu, the scan speed and atmosphere on the distortion, surface morphology and surface roughness have been investigated. The experiment also investigated the role of adding W particles to the Fe—Cu mixture. The result shows that adding W particles can reduce part distortion. To find the effect of gas protection in laser sintering, the three-dimensional specimens fabricated in both air and N2 atmosphere are also compared.

Abstract:

Direct Metal Selective Laser Sintering (DMSLS) is a layer-by-layer additive process for metal powders, which allows quick production of complex geometry parts. The aim of this study is to analyse the improvement of DMSLS with “EOSINT M270”, the new laser sintering machine developed by EOS. Tests were made on sintered parts of Direct Metal 20 (DM20), a bronze based powder with a mean grain dimension of 20 μm. Different properties and accuracy were evaluated for samples manufactured with three different exposure strategies. Besides mechanical properties, the manufacturing process was also examined in order to evaluate its characteristics. The quality of laser sintered parts is too affected by operator experience and skill. Furthermore, critical phases are not automatic and this causes an extension of time required for the production. Due to these limitations, DMSLS can be used for Rapid Manufacturing, but it is especially suitable to few sample series.

Abstract:

The purpose of this paper is to realize some researches concerning the powder Co-Cr, the sintering compacts obtain after Direct Metal Laser Sintering manufacturing and the corrosion resistance in artificial saliva. The Co-Cr alloys are used frequently in dentistry to realize personalized dental crown, bridges, chapels, dental implants or microsurgery instruments. The Co-Cr powders are used in Direct Metal Laser Sintering technologies to obtain personalized dental crown with complex forms after a ”stl” file, realized after a tomography or oral scanning. Direct Metal Laser Sintering process is used to realize quickly a scale model of physical part or assembly using 3D computer aided design CAD data. This alloy must present good corrosion behavior and mechanical resistance to be used in medical domain.

Abstract:

La Sinterizzazione Diretta di Metalli mediante Laser (DMLS), basata su un processo strato-per-strato, è stata usata per ottenere provini in leghe Co–Cr–Mo–W e Ti-6Al-4V per applicazioni biomediche. La risposta meccanica e la microstruttura sono state studiate sia nello stato “tal quale” che dopo trattamento termico post-produzione per i campioni in Co–Cr–Mo–W, e dopo due diversi trattamenti termici per quelli in Ti-6Al-4V. Misure di rugosità e durezza, così come test di trazione e flessione, sono state eseguite per studiare la risposta meccanica, mentre la diffrazione di raggi X, la microscopia elettronica (SEM, TEM, STEM) e la microanalisi (EDX) sono state usate per investigare la microstruttura. Nella lega Ti-6Al-4V è stata studiata anche l’anisotropia.I risultati nella lega Co–Cr–Mo–W mostrano una rete di lamelle ε-Co (esagonale) nella matrice γ-Co (cubica a face centrate), responsabile della alta resistenza a trazione (UTS) e durezza nello stato “tal quale”. I trattamenti termici aumentano la frazione volumica dell’ε-Co, modificando leggermente la dimensione media della struttura lamellare. In ogni caso, i trattamenti termici danno origine ad un sensibile aumento di UTS e durezza e ad una forte riduzione della duttilità. Quest’ultima è attribuito ad una massiccia precipitazione di fase esagonale Co3(Mo,W)2Si e alla contemporanea formazione di inclusioni ricche in Si.I campioni di Ti-6Al-4V rivelano una bassa porosità ed alte proprietà meccaniche, in particolare una maggiore elongazione rispetto ai dati di letteratura. Non si evidenzia alcuna anisotropia fre le orientazioni. La microstruttura osservata è molto fine. Si rileva una fase martensitica α’-Ti dopo il primo trattamento di rilassamento degli sforzi, mentre il ciclo termico induce una fase stabile α+β-Ti, con la fase β che cresce al bordo-grano della α.Questi risultati suggeriscono possibili applicazioni innovative della tecnologia DMLS per la produzione di parti meccaniche in campo medico/odontoiatrico.
Direct Metal Laser Sintering (DMLS), based on a layer-by-layer production process, was used to produce specimens in Co–Cr–Mo–W and Ti-6Al-4V alloys, which are utilized in biomedical applications. The mechanical response and microstructure were investigated in the as-sintered state and after post-production thermal treatments for the Co-Cr-Mo-W samples, and after two post-production treatments for the Ti-6Al-4V ones. Roughness and hardness measurements, as well as tensile and flexural tests, were performed to study the mechanical response, while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) and microanalysis (EDX) were used to investigate the microstructure in different conditions. The anisotropy of the Ti-6Al-4V specimens was also investigated. Results on the Co-Cr-Mo-W samples showed an intricate network of ε-Co (hcp) lamellae in the γ-Co (fcc) matrix, responsible of the high UTS and hardness in the as-sintered state. Thermal treatments increase volume fraction of the ε-Co (hcp) martensite but slightly modify the average size of the lamellar structure. Nevertheless, thermal treatments are capable of producing a sensible increase in UTS and hardness and a strong reduction in ductility. These latter effects were mainly attributed to the massive precipitation of an hcp Co3(Mo,W)2Si phase and the contemporary formation of Si-rich inclusions. Ti-6Al-4V specimens reveal extremely low porosity, high mechanical properties, in particular an elongation higher than the literature data. The results do not evidence any anisotropy between the different orientations. The observed microstructure is very fine. A martensitic α’-Ti phase is detected after the first stress relieving treatment, while the firing cycle induces a phase transformation to a stable α+β-Ti phase with the β phase growing at the α grains boundaries. These results suggest possible innovative applications of the DMLS technique to the production of mechanical parts in the medical and dental fields.

Abstract:

La definizione di "rapid prototyping" è ben nota. Ci si riferisce a quell'insieme di tecnologie utilizzate per la realizzazione di oggetti partendo da modelli geometrici molto complicati, realizzando protitipi direttamente dal disegno CAD 3D. Le tecnologie RP sono state poi sviluppate per l'industria artigianale, nell'obiettivo di accelerare la produzione senza perdita di precisione nella costruzione. Tra queste tecniche sono sorte quelle di selective laser sintering.La sinterizzazione è il processo termico e meccanico per produrre materiali compattando sostanze in polvere, sotto una certa pressione o temperatura; più precisamente, nella sinterizzazione laser le polveri sono riscaldate per un tempo brevissimo.La fisica che descrive questo processo è piuttosto articolata, dato che la descrizione parte dall'assorbimento di radiazione laser e che comprenderà conduzione termica nella polvere, trasformazione di fase di un materiale eterogeneo, formazione di fase solida con diversi meccanismi di condensazione e lo sviluppo delle diverse microstrutture dell'acciaio.Il lavoro sperimentale che è stato svolto è la produzione di una polvere di acciaio e vanadio utilizzabile in solid state sintering, ma dato quanto detto, lo studio ha incluso una descrizione più generale del processo della sinterizzazione metallica da polveri.Nel corso del lavoro si è contribuito alla messa a punto della stampante 3D per sinterizzazione di polveri metalliche realizzata alla 3d4mec, soffermandosi nella ricerca dei parametri ottimali per la stampa di polvere StainlessSteel CX by EOS.

Abstract:

Manufacturing functional prototypes and tools using conventional methods usually is a time consuming procedure with multiple steps. The pressure to get products to market faster has resulted in the creation of several Rapid Prototyping (RP) techniques. However, potentially one of the most important areas of Rapid Manufacturing (RM) technology lies in the field of Rapid Tooling (RT). Layer manufacture technologies are gaining increasing attention in the manufacturing sector for the production of polymer mould tooling. Layer manufacture techniques can be used in this potential manufacturing area to produce tooling either indirectly or directly, and powder metal based layer manufacture systems are considered an effective way of producing rapid tooling. Selective Laser Sintering (SLS) is one of available layer manufacture technologies. SLS is a sintering process in which shaped parts are built up layer by layer from bottom to top of powder material. A laser beam scans the powder layer, filling in the outline of each layers CAD-image, and heats the selected powder to fuse it. This work reports the results of an experimental study examining the potential of layer manufacturing processes to deliver production metal tooling for manufacture of polymer components. Characterisation of indirect selective laser sintering and direct selective laser sintering to provide the metal tooling is reported. Three main areas were addressed during the study: mechanical strength, accuracy, and build rate. Overviews of the results from the studies are presented. Two materials (RapidSteel 2.0 and special grade of highspeed steel) and also two generations of SLS machines Sinterstation 2000 and sinterstation research machine, which was constructed in Leeds) were used during this work.

Abstract:

This master’s thesis deals with the possibility of manufacturing gas analyzer by Rapid Prototyping Technology and it with the method Direct Metal Laser Sintering. The theoretical part describes the current production of component in the Frentech Aerospace LLC and innovation with the DMSL method in the company Innomia Furthermore JSC. Then an analysis of the principle of single methods Rapid Prototyping, especially the method of Direct Metal Laser Sintering, is implemented. The aim of the experimental part is to compare the mechanical properties and material structures, conventional metallurgy and powder metallurgy. The thesis also contains a technical-economic evaluation comparing the manufacture of mechanical part by conventional and advanced additive technology.

Abstract:

Thesis (Ph.D.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 15, 2006) Vita. Includes bibliographical references.

Abstract:

Ti-6Al-4V alloy has been used as biomedical implants for decades because of its superior mechanical properties, good biocompatibility, lack of allergic problems and good corrosion resistance. It is widely used as the tibial components in total knee arthroplastry and hip cup in total hip replacement. However, the mechanical properties of Ti-6Al-4V implant can be deteriorated due to corrosion pits. In the past decades, the rapid developments in additive manufacturing have broadened their applications in biomedical area due to the high geometrical freedom in fabricating patient-friendly implants. However, the high-localized thermal input and fast cooling rate during laser processing usually result in non-equilibrium phase with high residual stress. Therefore, it is necessary to apply proper post-treatments on the as-printed parts to ensure better properties. In this work, various post-treatments (e.g. post-heat treatments, hot isostatic pressing) were applied aim to improve the corrosion behavior of direct metal laser sintered Ti-6Al-4V parts. The effect of post-treatment temperature on the mechanical properties and corrosion behavior were examined experimentally. A discussion on factors influencing corrosion rate was presented, and the corrosion mechanism on the Ti-6Al-4V part in simulated body fluid was proposed. Based on the electrochemical measurement results, enhanced corrosion resistance was observed in the samples after high temperature HIPing at the annealing temperature (α+β region) of 799°C.

Abstract:

15-5PH stainless steel is an important alloy in the aerospace, chemical, and nuclear industries for its high strength and corrosion resistance at high temperature. Thus, this material is a good candidate for processing development in the direct metal laser sintering (DMLS) branch of additive manufacturing. The chemistry and microstructure of this alloy processed via DMLS was compared to its conventionally cast counterpart through various heat treatments as part of a characterization effort. The investigation utilized optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and glow discharge atomic emission spectrometry (GDS) techniques. DMLS processed samples contained a layered microstructure in which the prior austenite grain sizes were relatively smaller than the cast and annealed prior austenite grain size. The largest of the quantifiable DMLS prior austenite grains had an ASTM grain size of approximately 11.5-12 (6.7?m to 5.6?m, respectively) and the cast and annealed prior austenite grain size was approximately 7-7.5 (31.8?m to 26.7?m, respectively), giving insight to the elevated mechanical properties of the DMLS processed alloy. During investigation, significant amounts of retained austenite phase were found in the DMLS processed samples and quantified by XRD analysis. Causes of this phase included high nitrogen content, absorbed during nitrogen gas atomization of the DMLS metal powder and from the DMLS build chamber nitrogen atmosphere. Nitrogen content was quantified by GDS for three samples. DMLS powder produced by nitrogen gas atomization had a nitrogen content of 0.11 wt%. A DMLS processed sample contained 0.08 wt% nitrogen, and a conventionally cast and annealed sample contained only 0.019 wt% nitrogen. In iron based alloys, nitrogen is a significant austenite promoter and reduced the martensite start and finish temperatures, rendering the standard heat treatments for the alloy ineffective in producing full transformation to martensite. Process improvements are proposed along with suggested future research.
M.S.M.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering

Abstract:

Published Article
Rapid Manufacturing (RM) has emerged over the past few years as a potential technology to successfully produce patient-specific implants for maxilla/facial and cranial reconstructive surgeries. However, in the area of spinal implants, customization has not yet come to the forefront and with growing capabilities in both software and manufacturing technologies, these opportunities need to be investigated and developed wherever possible.The possibility of using Computed Tomography (CT) and Rapid Manufacturing (RM) technologies to design and manufacture a customized, patient-specific intervertebral implant, is investigated. Customized implants could aid in the efforts to reduce the risk of implant subsidence, which is a concern with existing standard implants. This article investigates how accurately the geometry of a customized artificial intervertebral disc (CAID) can represent the inverse geometry of a patient's vertebral endplates. The results indicate that the endplates of a customized disc implant can be manufactured to a calculated average error of 0.01mm within a confidence interval of 0.022mm, with 95% confidence, when using Direct Metal Laser Sintering.

Abstract:

DMLS (Direct Metal Laser Sintering), an additive manufacturing technology, is increasingly becoming popular to build intricate high quality functional parts & rapid prototypes. DMLS technology uses a high intensity laser to build components layer by layer, directly from metal powder. CAD data is directly converted to part without the need for tooling. It is possible to build internal features and passages that are not possible in conventional manufacturing routes. The process generates significant amount of condensate due to vaporization and suction applied to build chamber. Typically as much as 30% of the weight of powder ends up as condensate. The condensate so generated cannot be directly recycled. This results in significant reduction in profitability and process efficiency. This study pertains to 18% Ni Maraging Steel grade C300, which commonly used in DMLS process. Maraging Steel is used extensively to build functional parts by DMLS process especially for Tool and Die applications. In the present study chemistry, particle size distribution & morphology of the condensate was studied & compared with the powder. Parts were built using condensate and chemical, physical, mechanical, microstructure and XRD studies were done. These properties were compared with properties of parts built using fresh powder. No difficulty was encountered in building parts using condensate. However, hardness and tensile properties were found to be inferior, thus it is not possible to recycle the condensate directly. Present research investigates the cause of difference in these properties.

Abstract:

Abstract Direct Metal Laser Sintering (DMLS) technique is one of the technologies which is generally used to built prototypes and tooling applications. DMLS uses powder bed fusion to bond particles together by laser energy. A new powder layer is spread on top of the previous layers and the process is repeated up to required shape of part can be produced. This review paper presents development, current status and challenges of the DMLS technique with emphasises on material processed by DMLS and is aimed to understand influence of density, microstructure, micro-hardness, tensile strength and wear behaviour of built-up parts. It also highlights the process through proofs based on classical results in terms of advantages and applications.

Abstract:

Additive manufacturing (AM) is a type of manufacturing technologies whereby the material is added a layer upon layer to produce a 3D object. Produced 3D parts are applied in such industry sectors as space, aviation, automotive, building and has excellent future promises. Ourdays, the commercialy promised technique for metal manufacturing is Direct Metal Laser Sintering (DMLS). Our study concentrated on the investigation of the mechanical properties of produced17-4H (stainless steel) parts using DMLS. The effect of the DMLS process parameters (laser power, scanning speed and energy density) on the ultimate strength, yield strength and Young’s modulus was determined. We showed an evolution of the microstructure. The detected defects were classified. This study allowed to determine the optimal regimes of DMLS for SS 17-4H and describe mechanical properties of the produced parts as well as helped to show future possibilities of DMLS development.

Abstract:

This paper presents some practical considerations on finishing of parts made by direct metal laser sintering (DMLS). The main process capabilities limitations of this promising rapid tooling technique are in fact in the surface roughness of the produced parts. This fact hinders the introduction of DMLS as a widely employed industrial process, especially for what concerns the production of moulds and inserts and allows their use only as preseries tools in injection moulding of plastics, since the requirements for preseries tools are worse than those needed during the process. Barrel finishing, in turn, is a well established technique to improve the roughness of parts of complicated shape by means of a soft mechanical action over the surface. The results herewith presented show that it is possible to achieve roughness of the order of 1 μm Ra even when starting from initial roughness of the order of 15 μm Ra, i.e. those typically attained by DMLS.

Abstract:

Abstract Direct Metal Laser Sintering (DMLS) is a relatively new manufacturing process in additive manufacturing (AM) that fuses powdered metal by using a high-powered laser. Although this process allows manufacturing prototypes without requiring specific tooling, it is challenging to use this process for manufacturing high volume production parts since complex shapes can take a significant amount of build time. Furthermore, manufactured parts also need some amount of post-processing to remove the support material that may be required due to the layer-by-layer build process. This study investigates three process parameters that could be optimized to substantially reduce production time. These three parameters are as follows: build layer thickness, laser scan speed, and laser hatch distance. In order to evaluate the influence of these parameters, manufactured parts made of AISI 316L Stainless Steel are tested for fatigue life and static strength. A three-point bending test is used as per ASTM E466. While none of the three parameters is seen to significantly influence ultimate tensile strength, results indicate that build layer thickness is a significant process parameter that directly affects fatigue life. Furthermore, the interaction between build layer thickness and laser scan speed is found to be statistically significant for high cycle fatigue. However, laser scan speed and laser hatch distance are seen to be statistically insignificant for fatigue life. The initial results of this study indicate that process parameters of DMLS need to be selected judiciously in order to minimize build time while maintaining structural integrity.

Abstract:

Volcanogenic massive-sulfide (VMS) deposits may have had metal contributions from magmatic degassing and leaching of footwall rocks. The Windy Craggy Cu-Co-Zn VMS deposit in northwestern British Columbia may include magmatic contributions, based on laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of fluid inclusions (enriched in Sb, Sn, and Bi) and lithogeochemistry. Sulfide-mineral trace-element abundances in the massive-sulfide orebody, underlying stockwork zone, gold zone, and altered and unaltered mafic rock and argillite were analyzed by LA-ICP-MS. Elevated Au, W, As, Bi, Sb, Se, Te, Tl, Ag, Co, and Mo contents occur within the gold and/or stockwork zones. Increasing 'magmatic metals' with increasing Co/Ni values suggest direct magmatic contribution to the deposit. Covariation of Co with these so-called 'magmatic elements' indicates that it, too, may be of magmatic origin, sourced via fluids exsolved from a crystallizing magma; however, evidence from the composition of rocks and sulfide minerals from Windy Craggy and other VMS deposits suggests that there is probably no meaningful distinction between hydrothermal leaching and direct magmatic contributions and that most - if not all - fluids that form VMS deposits should be termed 'magmatic-hydrothermal'.