17 research outputs found

    Influence of scanning speed on the microhardness property of additive manufactured titanium alloy

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    Ti6Al4V is an important aerospace alloy, and it is challenging processing this material through traditional manufacturing processes. Laser metal deposition, an additive manufacturing process offers lots of advantages for processing aerospace materials, the ability to increase buy-to-fly ratio by at least 80% amongst other things. An improved property is achievable through laser metal deposition. The Ti6Al4V powder of particle size 150-200 μm was deposited using a 4.0 kW Rofin Sinar Nd: YAG laser on 72x72x5 mm Ti6Al4V substrate. The powder was delivered using argon gas as a shield. The scanning speed was varied between 0.01 and 0.12 m/sec. The  microstructures of the deposited layers were studied by optical microscope and the microhardness was also measured using the Vickers hardness tester. The properties of the deposited tracks were compared to that of the substrate. The microhardness was found to increase with increase in scanning speed.Keywords: Additive Manufacturing, Laser Metal Deposition, Microstructural  Characterization, Scanning speed, Titanium Allo

    Corrosion behaviour of laser additive manufactured titanium alloy

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    Abstract: The influence of process parameter on corrosion behavior of the most widely used titanium alloy-Ti6Al4V, produced using laser metal deposition process was studied. The processing parameters: scanning velocity, the powder flow rate and gas flow rate were kept at constant values of 0,005m/s, 1.44 g/min and 4 l/min while the laser power was varied between 0.8 to 3.0 kW. Electrochemical corrosion test was conducted on each of the samples produced at each set of processing parameters. The corrosive media used is the solution of sodium chloride (NaCl) desolved in deionized water. The results of this study indicate that the as the laser power was increase, the corrosion behaviour was found to be improved. The better corrosion resistance performance of the additive manufacture part can be attributed to the higher cooling rate that is associated with this type of manufacturing process. This high cooling rate results in the higher hardness of the material which could also contribute to the improved corrosion resistance behaviour

    Microstructural evolution of laser metal deposited 17-4 PH SS-tungsten composite with varying volume percent tungsten

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    Abstract: This study investigates the influence of quantity of tungsten powder on the microstructural evolution of 17-4 PH stainless steel-tungsten composite produced using laser metal deposition process. The 17-4 PH stainless steel and tungsten powders were deposited on 316 stainless steel substrate at laser power of 2600 W. The tungsten powder flow rate was varied between 0.5 rpm and 2.0 rpm while 17-4 PH stainless steel powder flow rate, the scanning speed, the gas flow rate and the laser spot size were fixed at 2.0 rpm, 0.5 m/s, 2.5 l/min and 2.0 mm respectively. Five (5) multiple track of 17-4 PH stainless steel and tungsten powder were deposited on 316 stainless steel of thickness 10 mm from different hopper at 50% overlapping percentage to produce 17-4 PH SS-W composite. During the microstructural study, it was observed that tungsten carbide has been precipitated in-situ and evenly dispersed in the 17-4 PH SS-W composite produced. SEM and EDS analysis also revealed the presence of BCC alpha (α) ferrite and FCC gamma (δ) ferrite with the presence of sigma (σ) phase precipitates

    Influence of laser power on microhardness and wear resistance properties of laser metal deposited 17-4 PH stainless steel

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    Abstract: This aim of this research is to investigate the impact of laser power on the hardness and the wear resistance properties of laser metal deposited 17-4 PH stainless steel. Hardness was studied using Zwick/Roell microhardness tester and the wear resistance property was carried out using ball-on-disc Anton Paar-tribometer wear tester. The study revealed that an irregular increase and decrease in the average hardness value and wear behaviour were observed. This could be attributed to the presence of copper precipitate which was more concentrate at the overlapping region because of the reheating activity that is happening between the succeeding and preceding track layers

    Advanced manufacture of compositionally composite graded materials : an overview

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    Abstract: Compositionally graded composite materials are advanced materials that consists of inhomogeneous composition as well as structure that varies across the entire volume and with changing properties. Functionally graded materials are produced through different manufacturing processes which include centrifugal method, powder metallurgy method, and additive manufacturing technology. Additive Manufacturing (AM) is an advanced manufacturing process used to produce three dimensional objects simply by adding materials in layers using the digital image of the component. In this chapter, the production of compositionally graded composite materials using an advanced manufacturing method, laser additive manufacturing technologies, which include selective laser melting/sintering and laser metal deposition/laser material deposition (LMD) processes are reviewed and the recent research progress are also presented

    Influence of laser power on microstructure of laser metal deposited 17-4 ph stainless steel

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    Abstract: The influence of laser power on the microstructure of 17-4 PH stainless steel produced by laser metal deposition was investigated. Multiple-track of 17-4 stainless steel powder was deposited on 316 stainless steel substrate using laser metal deposition, an additive manufacturing process. In this research, laser power was varied between 1.0 kW and 2.6 kW with scanning speed fixed at 1.2 m/s. The powder flow rate and the gas flow rate were also kept constant at values of 5 g/min and 2 l/min respectively. The microstructure was studied under optical microscope and it revealed that the microstructure was dendritic in structure with finer and lesser δ-ferrite at low laser power while the appearance of coarse and more δ-ferrite are seen at higher laser power

    Exercise and gallstone disease

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    Indication, effets et contre-indications de l'activité physique chez des patients souffrant de calculs biliaires. Effets de l'exercice sur les lipides, le cholestérol, chez les patients obèses exposés. Fonction et réponse de la vésicule biliaire à l'effort
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