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tungsten-carbide
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, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Electrodeposition of composite coatings containing nano particles is very important because this technique is simple and economic. In this research, in order to produce a coating with high hardness and wear resistance, Ni-Co/WC nano composite was co-deposited. Watt’s based bath containing cobalt and tungsten carbide was used and parameters such as preparation of solution, concentration of ingredients and current density were controlled and adjusted. Surface morphology, microstructure and mechanical properties of coatings were studied by SEM and AFM microscopes. Mechanism of electrodeposition was investigated by cyclic voltametry, cronoamperometry and cronopotentiometry techniques and...
Formation of ZrC-WC-W Composites Ceramics by DCP Method and Investigation of Their Physical Properties, Phase Composition and Microstructure
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor) ; Mirhabibi, Ali Reza (Supervisor)
Abstract
Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense...
Copper-cobalt/Tungsten Carbide Nano-composite Coatings Deposited on Pure Copper Substrate by Electrochemical Deposition
, M.Sc. Thesis Sharif University of Technology ; Abachi, Parvin (Supervisor) ; Dolati, Abolghasem (Supervisor)
Abstract
In this research a copper- Tungsten carbided nanocomposite coating prepared by electrodeposition from a sulfate bath in order to increase the hardness and erosion resistance of cooper without loosing cooper's specific physical properties as like as electrical and thermal conductivity. Various parameters were evaluated for finding significant factors in electrodeposition of Cu-Co/WC composite. Current density and concentration of WC and SDS were selected as affective factors. The morphology and structure were characterized by XRD and SEM. The mechanical properties of the coatings, such as hardness, wear resistance and surface roughness were studied with Vickers hardness indentation; pin on...
The Effect of Heat Treatment and Alloying Elements on Microstructure and Wear Resistance of Hadfield Steels
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Hadfiled steel was invented by Sir Robert Hadfield in 1882. Different types of this steel have been used widely in cement industry, mining, drilling and railroad ways due to its high toughness, high work hardening capacity and excellent wear resistance. Since the wear life of machineries and parts used in such industries is short and costly, time consuming service of the wear parts, there have been a lot of interest to increase wear resistance of austenitic manganese steels in recent years. In this study a new type of austenitic manganese steels with high carbon-high vanadium and high tungsten content has been introduced and effect of carbon, vanadium and tungsten on microstructure, micro...
Electrodeposition of Cu/WC Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor) ; Afshar, Abdollah (Supervisor)Cosintering of powder injection molding parts made from ultrafine WC-Co and 316L stainless steel powders for fabrication of novel composite structures
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1, January 2010, Pages 233-241 ; Petzoldt, F ; Sharif University of Technology
Abstract
Abstract Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (> 4 pct) is developed in the temperature range of 1080° C to 1350° C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the
The effect of current density on microstructural homogeneity, hardness, fracture toughness and electrochemical behavior of electrodeposited Cu-0.5Co/WC nano-composite coating
, Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3505-3511 ; 10263098 (ISSN) ; Abachi, P ; Dolati, A ; Sharif University of Technology
Abstract
The Cu-0.5Co/WC nano-composite coating was synthesized on CP-copper substrate using Direct Current (DC) electrodeposition method. In this work, it was tried to increase the hardness of surface without considerable degradation of copper's particular physical properties such as electrical conductivity. The effect of current density on microstructural homogeneity, hardness, fracture toughness, and electrochemical behavior of coating was investigated. The copper plates with the purity of 99.99% were used as electrodes. The electrolyte consists of tungsten carbide particles (30 g/l), copper sulfate (200 g/l), sulfuric acid (50 g/l), cobalt sulfate (50 g/l), and Sodium Dodecyl Sulfate (SDS) (0.3...
Numerical Simulation and Experimental Investigation of Powder Stream and Laser Attenuation in Fabrication of Functionally Graded Materials by Means of Laser Directed Energy Deposition Process
, Ph.D. Dissertation Sharif University of Technology ; Akbari, Javad (Supervisor) ; Moradi, Mahmoud (Co-Supervisor)
Abstract
Functionally Graded Material (FGM)is attaining more and more interests recently due to its outstanding feature of possessing benefits of physical and mechanical properties of two materials in one part. One of the common processes to fabricate FGM is laser directed energy deposition of pre-mixed powder of two materials. The powder stream and laser attenuation in LDED of FGM is studied in this dissertation by the aid of numerical simulation and experimental investigations. Due to numerical simulation results, which is done in FLUENT software, powder particle size and axial shielding gas flow rate has significant effect on composition of powder mixture falling into the molten pool. Considering...
Sintering viscosity and sintering stress of nanostructured WC-Co parts prepared by powder injection moulding
, Article Powder Metallurgy ; Volume 54, Issue 1 , Nov , 2011 , Pages 84-88 ; 00325899 (ISSN) ; Sharif University of Technology
2011
Abstract
The uniaxial viscosity and sintering stress of WC-10Co-0·9VC (wt-%) were obtained by a loading dilatometer as functions of fractional density (0·64<ρ<0·93) and temperature (1084
Sintering of nanostructured WC-10Co/316L stainless-steel composite parts made by assembling of the PIM parts
, Article World Powder Metallurgy Congress and Exhibition, World PM 2010, Florence, 10 October 2010 through 14 October 2010 ; Volume 4 , 2010 ; 9781899072194 (ISBN) ; Petzoldt, F ; Hartwig, T ; Veltl, G ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2010
Abstract
This paper reports co-sintering response of nanostructured WC-Co/316L stainless steel composite produced by assembling of powder injection molding (PIM) parts. A significant mismatch sintering shrinkage (>4%) was observed in the temperature range of 1080-1350 °C. The reaction between WC and Fe at the contact area resulted in the diffusion of C and Co into the iron lattice and eventually formation of a low-temperature liquid phase that in fact affects the shape control of the PIM parts during sintering. In order to make the co-sintering feasible, a special sintering cycle was developed. The reaction between the cemented carbide and stainless steel was also retarded by developing a special...
Effect of VC and (Ta, Nb)C on wear of WC-10Co based cemented carbides
, Article Tribology - Materials, Surfaces and Interfaces ; Volume 3, Issue 1 , 2009 , Pages 31-36 ; 17515831 (ISSN) ; Ganji, Y ; Sharif University of Technology
2009
Abstract
WC-Co cemented carbides, including small angular tungsten carbides particles, are used extensively to improve wear resistance. Some additives can affect mechanical and wear properties of these materials. In this study, the effect of VC and (Ta, Nb)C content on wear of WC- 10Co were considered. The tests were performed at normal load of 230 N and sliding distance of 800 m up to 3200 m. Wear tests were carried out using dry sand/rubber wheel apparatus. Wear rate, standard and modified wear coefficients were calculated. The microstructures of prepared specimens were examined by optical microscopy. The morphological analysis of the worn surfaces was made by SEM. The results show that VC content...
Production of net-shaped dense metal-carbide-based composites through an infiltration process at intermediate temperature
, Article International Journal of Refractory Metals and Hard Materials ; Volume 38 , 2013 , Pages 35-39 ; 02634368 (ISSN) ; Sani, M. A. F ; Shabani, K ; Bodaghi, M ; Sharif University of Technology
2013
Abstract
Tungsten composites are interesting materials for high temperature applications. These composites are conventionally produced by solid state reaction, where elevated temperatures and long sintering processes are inevitable, and generally produce volatile components that increase defects and impair the properties of the composites for high temperature applications. In the present paper, synthesis of dense near net-shaped transition metal-metal carbide by reaction casting is studied, which creates a potential application for the composite at 2000 C. Since the pores of the ceramic preform are filled with reaction products, this technique is referred to as displacive compensation porosity (DCP)....
Effect of carbon content on carbide morphology and mechanical properties of A.R. white cast iron with 10-12% tungsten
, Article Materials Science and Engineering A ; Volume 542 , April , 2012 , Pages 113-126 ; 09215093 (ISSN) ; Skandani, A. A ; Al Haik, M ; Sharif University of Technology
2012
Abstract
Carbide morphologies of white cast iron containing 22% Cr and 10-12% tungsten with different carbon contents (2.34-3.20. wt.%) were investigated. Results indicated that for the as-cast alloys with no heat treatments, the addition of carbon changes the morphology of carbides during air-cooling in the presence of tungsten. Light microscopy analysis revealed that for an alloy with 2.3. wt% carbon, chromium carbides possess coarse gray appearance (GA). Increasing the carbon content reduced the coarse GA zones volume fraction while a finer GA zones emerged. The coexistence of coarse and fine GA phases came to an end at 2.8. wt% carbon, at which only fine GA zones spread throughout the chromium...
Microstructure and mechanical properties of WC-10Co cemented carbide containing VC or (Ta, Nb)C and fracture toughness evaluation using different models
, Article International Journal of Refractory Metals and Hard Materials ; Volume 31 , 2012 , Pages 141-146 ; 02634368 (ISSN) ; Abachi, P ; Simchi, A ; Sharif University of Technology
Abstract
This article describes a study on WC-10Co cemented carbides with different percent of grain growth inhibitors. Samples were prepared by the conventional powder metallurgy method, using WC and Co powder and different concentrations of VC and (Ta, Nb)C powder. All samples were processed using a hot isostatic press (HIP) and the effect of grain growth inhibitors on the microstructure and mechanical properties were investigated. Additionally, microstructure and powder particle morphology were examined using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). The specimen's microstructure proved that the addition of VC is more effective at suppressing grain growth than...
Electrodeposition of Ni/WC nano composite in sulfate solution
, Article Materials Chemistry and Physics ; Volume 129, Issue 3 , 2011 , Pages 746-750 ; 02540584 (ISSN) ; Dolati, A ; Rezagholibeiki, S ; Sharif University of Technology
Abstract
Metal matrix composite coatings have gained great attention due to their exclusive properties. They have shown the properties of a metallic host material modified by addition of a second phase. In electrodeposition of Ni/WC nano composite, nickel was deposited on the substrates by DC electrodeposition in Watt's based bath containing nickel sulfate, nickel chloride, boric acid and sodium dodecyl sulfate. WC content in the coating was determined by different parameters such as current density, powder content and surfactant amount. Mechanism of electrodeposition was analyzed by cyclic voltammetry and was confirmed by Guglielmi model. Surface morphology was studied by scanning electron...
A comparison between the corrosion resistances of High Velocity Oxy Fuel (HVOF) sprayed coatings and hard chromium coatings
, Article Materials Science Forum, 1 September 2010 through 3 September 2010, Seoul ; Volume 673 , 2011 , Pages 173-178 ; 02555476 (ISSN) ; 9783037850183 (ISBN) ; Khameneh Asl, S ; Vasfpour, R ; Tazesh, F ; Khallagi, P ; Sharif University of Technology
2011
Abstract
HVOF-sprayed coatings (WC-17%Co) and hard chromium coatings corrosion resistances have been compared through electrochemical polarization test in 3.5% NaCl solution. WC-17%Co alloy coatings were deposited on mild steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. The layers of standard and crack free hard chromium coatings were prepared by using Direct Current (DC) and Pulse Current (PC) electroplating process on the mild steel substrates. Hard chromium coatings was characterized as a reference material, to verify whether HVOF-sprayed coatings are suitable as a hard chromium coatings replacement. The microstructure of the coatings was examined by OM, SEM and XRD. Standard hard...
Al2O3-ZrO2 nanostructured coatings using DC plasma electrolytic oxidation to improve tribological properties of Al substrates
, Article Applied Surface Science ; Volume 356 , November , 2015 , Pages 927-934 ; 01694332 (ISSN) ; Meletis, E. I ; Golestani Fard, F ; Yerokhin, A ; Rastegari, S ; Faghihi Sani, M. A ; Sharif University of Technology
Elsevier
2015
Abstract
Alumina-zirconia nanostructured coatings were formed on 7075 Al alloy through Plasma Electrolytic Oxidation (PEO) operated in aDC potentiostatic mode. The composite coatings were produced in the range of 425-500 V in an alkaline electrolyte containing 4 g/LK2ZrF6. Tribological properties of coatings were investigated using dry sliding wear test against WC balls with a pin-on-disc tribometer. Wear rates were evaluated using optical profilometer. It was shown that the nanostructured alumina-zirconia composite coatings can be formed at voltages 450 V. The coating thickness and roughness were in the range of 15.2-24.2 μm and 0.68-2.35 μm, respectively. The distribution of Al, Zr and O in the...
Microstructure and segregation behaviour of directionally solidified tungsten bearing 25Cr-35Ni-Nb heat-resistant stainless steels
, Article International Journal of Cast Metals Research ; Volume 30, Issue 2 , 2017 , Pages 112-122 ; 13640461 (ISSN) ; Karimi Taheri, A ; Varahram, N ; Davami, P ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
Two series of heat-resistant 25Cr-35Ni-Nb stainless steels with tungsten addition and Nb/C ratio of ≈2.6 and 3.9 were directionally solidified under two cooling rates of 23–6 °C s−1, respectively. EDS analysis, electron backscatter diffraction (EBSD), differential thermal analysis (DTA) and field emission scanning electron microscopy (FESEM) tests were carried out to show that tungsten as a carbide phase nucleant promoted weak coupled eutectic growth of γ/ M7C3 and decreased the lamellar eutectic colonies. Substantial negative segregation of Ni and Fe and positive segregation of Nb and Cr in tungsten-bearing alloys stimulated the γ/M23C6 reaction and the M23C6 possessed a dendritic...
Experimental modeling and optimizing process parameters in the laser assisted machining of silicon carbide particle-reinforced aluminum matrix composites
, Article Materials Research Express ; Volume 6, Issue 8 , 2019 ; 20531591 (ISSN) ; Movahhedy, M. R ; Khodaygan, S ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
The process of laser assisted machining (LAM) of metal matrix composites (MMC) is experimentally studied. The effects of process parameters (cutting speed, feed rate and depth of cut), laser parameters (laser power, laser frequency and laser beam angle), and the percentage of reinforcing particles on the tool wear and the surface roughness are investigated. Furthermore, the effects of the mentioned parameters on the built-up edge (BUE), chip shape, and workpiece temperature are explored. The experiments were performed using uncoated tungsten carbide and PCD tools under dry conditions. In order to analyze the sensitivity of the process parameters, the Plackett-Burman method was used for...
Study of cemented carbonitrides with nickel as binder: Experimental investigations and computer calculations
, Article International Journal of Refractory Metals and Hard Materials ; Volume 31 , 2012 , Pages 164-170 ; 02634368 (ISSN) ; Abachi, P ; Parvin, N ; Pourazrang, K ; Sharif University of Technology
2012
Abstract
Cobalt is the most common binder in cemented carbides industry. However, there are some interests in use of alternatives. The similarity in properties has made nickel the first choice. In the present work, the effect of initial composition on modern hardmetals containing transition metal carbides/carbonitrides that are called "cemented carbonitrides" with nickel as binder was investigated. Change in quantity of additive carbides and tungsten to carbon (C/W) weight ratio through applying metallic tungsten powder in primary powder mixture had some effects on final hardness, transverse rupture strength, and microstructure of studied alloys. Addition of vanadium carbide not more than 0.2 wt.%,...