Experimental and numerical analysis of geometrical properties of laser metal deposited titanium
- Authors: Akinlabi, Esther Titilayo , Tayob, Mohammed A. , Pietra, Francesco
- Date: 2016
- Subjects: Ansys , Heat-Affected zone , Laser metal deposition , Microhardness , Microstructure , Porosity , Powder flow rate , Titanium
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93300 , uj:20330 , Citation: Akinlabi, E.T., Tayob, M.A. & Pietra, F. 2016. Experimental and numerical analysis of geometrical properties of laser metal deposited titanium.
- Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this paper, the laser metal deposition process was modelled in ANSYS Parametric- Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is, the width and the height of the resulting clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder flow rate, which was varied between 0.5-2.5g/min. In addition to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples with the exception of the clad deposited at the lowest powder flow rate setting of 0.5 g/min. An increase in the powder flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample produced with the highest powder flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti- 6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness.
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Properties of pervious concrete for hydrologic applications
- Authors: Ekolu, Stephen O. , Diop, Souleymane , Azene, Firehiwot
- Date: 2016
- Subjects: Pervious concrete , Compressive strength , Porosity
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/214004 , uj:21224 , Citation: Ekolu, S.O., Diop, S & Azene, F. 2016. Properties of pervious concrete for hydrologic applications.
- Description: Abstract: This paper presents an experimental investigation that was conducted to examine those properties of interest with regard to the passage of water through pervious concrete. A total of 30 mixtures of pervious concrete were prepared at water-cementitious ratios (w/cm) varied from 0.25 to 0.40. Three aggregate types and sizes were used consisting of 13.2, 9.5 and 6.7 mm granite stone; 6.7 mm shale and 9.5 mm dolomite. Pozzolans were incorporated into mixtures in proportions of 20, 30 and 50% fly ash (FA) or 30% and 50% ground granulated blast furnace slag (GGBS). Compressive strength development in the mixtures was monitored at 7, 14, and 60 days. It was found that strength gain after 14 days generally occurred only in mixtures containing pozzolans. A unique behavior in property relations of pervious concrete was found with compressive strength increasing and porosity decreasing with increase in w/cm, contrary to established knowledge of conventional concrete properties. It was found that mixtures made with 6.7 or 9.5 mm granite stone gave porosity and permeability characteristics that were most suitable for hydrologic applications. Similarly, incorporation of 20% FA, 30% or 50% GGBS in the mixtures gave the most appropriate mechanical and transport properties.
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Laser metal deposition of Ti6Al4V/Cu composite : a study of the effect of laser power on the evolving properties
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2014
- Subjects: Porosity , Laser metal deposition , Titanium alloys
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/375937 , uj:4740 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11726
- Description: A study of the effect of laser power was investigated over the volume of deposited composite, microstructure and microhardness. The laser power was varied between 600 and 1800 W while keeping all other parameters constant. An indication shows that the area and the volume of the deposited composites are directly proportional to the laser power employed. The volume of the deposit obtained falls between 358.6 mm3 and 1009 mm3. The microstructures were analyzed and found that the formation of the Widmanstatten structures improved the hardness of Ti6Al4V/Cu composites. The hardness values of the deposits varied between HV335 and HV490. The percentages of porosities of the samples were also presented and found to have an inverse relationship with the laser power. The results are presented and discussed.
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Effect of scanning speed and powder flow rate on the evolving properties of laser metal deposited ti-6al-4v/cu composites
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2016
- Subjects: Hardness , High pfr , Laser metal deposition , Microstructure , Porosity , Volume of deposited composite
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/93307 , uj:20331 , Citation: Erinosho, M.F., Akinlabi, E.T. & Pityana, S. 2016. Effect of scanning speed and powder flow rate on the evolving properties of laser metal deposited ti-6al-4v/cu composites.
- Description: Abstract: In Laser Metal Deposition (LMD), good bonding between two similar or dissimilar materials can be achieved if the interrelationships between the processing parameters are well understood. LMD samples of titanium alloy, Ti-6Al-4V and copper, Cu were produced by varying the scanning speed and keeping other parameters constant. The deposited samples were characterized through the volume of deposited composites, microstructure, microhardness and the degree of porosity. The effect of the optimized high (powder flow rate) PFR, scanning speed varying from 0.06 m/min to 1.2 m/min and a constant power of 1kW led to a degree of porosity on the deposited composites. The varying percentages of porosities in the samples have an advance merit effect in the implantation of bones in animal and human. It was found that the existence of pores reduced as the scanning speed increases. The Vickers mirohardness was observed to increase with an increase in the scanning speed which shows an improvement in the properties of the Ti-6Al-4V/Cu composites. At low scanning velocity, the microstructure appears coarse due to the high rate of powder deposited at the same power of 1kW. The α-phase acicular microstructure decreases in size and thickness with an increase in the scanning speed. Widmanstätten structure was found in the scanning electron microscopy analyses. The results show that high PFR and low scanning speed have significantly influenced the evolving properties of the deposited composites.
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Characterizing the effect of processing parameters on the porosity of laser deposited titanium alloy powder
- Authors: Mahamood, Rasheedat M. , Akinlabi, Esther Titilayo , Shukla, Mukul , Pityana, Sisa
- Date: 2014
- Subjects: Laser metal deposition , Medical implants , Porosity , Processing parameters , Titanium alloy
- Type: Article
- Identifier: uj:4739 , ISSN 2078-0966 , http://hdl.handle.net/10210/11725
- Description: Laser Metal Deposition (LMD) is an additive manufacturing technique that produces parts layer by layer directly from the Computer Aided Design (CAD) file. Highly customized parts with complex shapes such as medical implants can well be manufactured using the LMD process. LMD has been used to produce a wide range of patient specific (customized) parts. Porous parts are of particular importance as medical implants because they can potentially aid the healing process and proper integration of the implant with the body tissues. In this research porous samples of titanium alloy (Ti6Al4V) were produced using the LMD process. Spherical shaped Ti6Al4V powder of particle size ranging between 150 to 200 μm was used. The effect of laser power and scanning speed on the shape, size and degree of porosity of the deposited tracks was investigated. The results showed that as the laser power was increased and the scanning speed decreased, the degree of porosity was reduced. The size of the porosity was also found to reduce as the laser power was increased.
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Influence of process parameters on porosity behaviour of laser metal deposited titanium composites
- Authors: Ogunlana, Musibau O. , Akinlabi, Esther Titilayo
- Date: 2016
- Subjects: Boron carbide , Laser power , Porosity
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/214397 , uj:21276 , Citation: Ogunlana, M.O & Akinlabi, E.T. 2016. Influence of process parameters on porosity behaviour of laser metal deposited titanium composites.
- Description: Abstract: This research paper reports the effect of laser power on the degree of porosity of the deposited tracks and characterized the specific porous structure. The results revealed that as the laser power was increased, the degree of porosity was however reduced. Prior the characterization process, titanium alloy and boron carbide (Ti6Al4V-B4C) composites powder were deposited on Ti6Al4V substrate using laser metal deposition (LMD) process through the application of Ytterbium fibre laser system. The laser power was varied between 800 W and 2400 W at interval of 200 W while all other process parameters were kept constant. The maximum capacity of this laser system is 3.0 KW which provides beam size of 4 mm for the control characterization of the deposited samples. After the deposition process, the samples were sectioned for porosity analysis and microstructural studies. The sectioned samples were however mounted, ground and polished according to standard metallurgical preparation of titanium alloys. The polished samples were then etched using Kroll’s reagent. Porosity analysis was observed using the optical microscope equipped with Analysis Docu Image Processing Software (ADIPS) to establish the percentage porosity and the maximum pore sizes of the composites...
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Investigation the effect of porosity on corrosion resistance and hardness of wc-co coatings on metal substrates
- Authors: Oladijo, O.P. , Obadele, B.A. , Venter, A.M. , Cornish, L.A.
- Date: 2016
- Subjects: Porosity , HVOF , Thermal spray
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/215160 , uj:21371 , Citation: Oladijo, O.P. et al. 2016. Investigation the effect of porosity on corrosion resistance and hardness of wc-co coatings on metal substrates.
- Description: Abstract: Porosity is an important coating feature which strongly influences coating properties. Porosity creates poor coating cohesion and allows for higher corrosion rate and wear, and is generally associated with a higher number of unmelted or solidified particle that become trapped in the coating [1]. This investigation was conducted to investigate the effect of porosity on the hardness and corrosion resistance of WC-17Co coating on metal substrates. Coating of about 200μm were successful deposited by HVOF techniques unto four metal substrates, namely brass, 304L stainless steel, super-invar and aluminium. The corrosion behaviour was examined in chloride medium using direct current (DC) polarization test. The Vickers hardness was undertaken at loads of 5 kg for 10 s. The microstructures of the coatings were studied before and after the corrosion tests by scanning electron microscopy with EDX. The results indicated a strong correlation between porosity and corrosion rate, as well as hardness of the WC-17Co coatings.
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A simulation study of methane-hydrogen gas mixture permeation through nanoporous palladium membrane using molecular dynamics
- Authors: Oyinbo, Sunday Temitope , Jen, Tien-Chien , Gao, Qingwei , Lu, Xiaohua
- Date: 2020
- Subjects: Molecular Dynamics , Porosity , Palladium membrane
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/460667 , uj:41003 , Citation: Oyinbo, S.T. et al. 2020. A simulation study of methane-hydrogen gas mixture permeation through nanoporous palladium membrane using molecular dynamics.
- Description: Abstract: We conducted molecular dynamic (MD) calculations to explore the efficiency of H2/CH4 separation through nanoporous palladium membrane. A palladium membrane with engineered-porosity of 0.1% to 2.2% is used in our model of gas component separation from a mixture. We use computations of molecular dynamics to measure many trajectories of the molecules and thereby collect low statistical uncertainty projections of the gas flow rates. Our simulations demonstrate that high porosity palladium membranes are permeable to both gasses. As the porosity decreases, the permeability of larger molecules greatly reduced, which contributes to an exclusion effect of molecular size for a range of porosity that can permit smaller molecules. This implies that the determined porosity can achieve high selectivity in the separation of gas molecules while the desired gas molecules exhibiting high permeability. We also found that external driving force has...
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