Papers by Keyword: Composite Powders

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Authors: Yan Bao Li, Dong Xu Li, Wen Jian Weng
Abstract: Biphasic tricalcium phosphate (BTCP) powders composed of α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP) were prepared using amorphous calcium phosphate (ACP) precursor after heat treatment at 800oC. The in vitro dissolution behavior of the powders was examined after soaked in 0.1M NaAc-HAc buffer solution for different times. It was revealed that the Ca2+ and PO4 3- concentration, and pH value of the BTCP-soaked solution are higher than those of the α-TCP- and β-TCP-soaked solutions. The dissolution behavior of BTCP powders was explained. The specific dissolution behavior of BTCP powders can widen the biodegradation range of calcium phosphate family.
Authors: Riho Tarbe, Priit Kulu, Arkadi Žikin, Andrei Surženkov
Abstract: The aim of the current study was to elaborate and compare abrasive wear resistance of thick metal matrix based deposited coatings. To produce metal matrix composite (MMC) coatings, experimental powders made by mixing commercial nickel and iron based powders with recycled hardmetal powder were used. The usage of recycled hardmetal as an initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Based on structural studies the optimal content of 40 vol% hard phase was selected. Plasma transferred arc (PTA) hardfacing and high velocity oxyfuel (HVOF) spraying were used as deposition technologies. The behavior of coatings by abrasive rubber wheel wear (ARWW ) (based on G 65 standard), abrasive impact wear (AIW) and abrasive erosion wear (AEW) (based on GOST standard) was investigated. The results showed that the wear resistance of experimental PTA hardfacings at high angle impact wear conditions is notably higher than of HVOF sprayed coatings.
Authors: Kyung Ho Min, Si Young Chang, Deok Soo Kim, Ji Soon Kim, Young Do Kim
Abstract: The aging behavior of sintered Al composites with various ceramic contents was investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0 wt.% and 5 wt.%. The blended powders were compacted at 250 MPa. The sintering process was performed at 620oC for 60 min in a N2 atmosphere. After sintering, each part was solution-treated at 518oC for 60 min and aged at 180oC. The Rockwell hardness value at the peak aging time increased with increased ceramic contents. However, the peak aging time at maximum hardness was reduced with increased ceramic contents. The changes in aging behavior may have been caused by the acceleration of diffusion due to the strain induced by differences in the thermal expansion coefficients of the matrix and the ceramic phases.
Authors: Asma Salman, Brian Gabbitas, De Liang Zhang, Peng Cao, Stiliana Raynova
Abstract: A feedstock of Ti(Al,O)-Al2O3 composite powders was produced by high energy milling of a mixture of Al and TiO2 powders followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity oxygen-fuel (HVOF) technique on H13 steel substrates to produce Ti(Al,O)-Al2O3 composite coatings. The performance of the coatings was assessed in terms of thermal fatigue behaviour and reaction with molten aluminium (soldering). The composite powders and coatings were characterised using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses characteristics and potential applications of the composite coatings.
Authors: Liang Zhao, Qun Hu Xue, Dong Hai Ding
Abstract: MgO-Al2O3-ZrO2 composite powders with 3 kinds of mass ratio were synthesized by sol–gel method using MgCl2·6H2O, AlCl3·6H2O and ZrOCl2·8H2O as starting materials, and NH3·H2O as a precipitant. The composite powders which match with zirconium oxide particle size and evenly distribute can are advantageous to the formation of metastable t-ZrO2 and restrain the grain growth as the additive of modified sizing nozzle. Chemical composition, mineral phase, particle size distribution and micro-morphology of the composite powders were investigated by X-ray fluorescence instrument, X-ray diffractometer, laser particle size analyzer and scanning electron microscope. Research showed that under the process that the concentration of MgCl2 solution 0.2 mol/L, AlCl3 and ZrOCl2 solution concentration 0.5 mol/L, the pH controlled between 10 ~ 11, PEG as the surfactant, drying at 70°C±5°C, heat treatment temperature at 800°C for 3h, particle size distribution of MgO-Al2O3-ZrO2 composite powders were: d10 = 1.28 μm, d50 = 4.65μm, d90 = 11.13μm (MgO 10%); d10 = 1.15μm, d50 = 5.80μm, d90 = 15.13μm (MgO 15%);d10 = 1.21μm, d50 = 6.59μm, d90 = 16.87μm (MgO 20%). With the rising of heat treatment temperature, the crystallization degree of composite powders increased, at 800 °C a small amount of t - ZrO2 precipitated, meanwhile MgO and Al2O3 are still in the amorphous phase. The MgO-A12O3-ZrO2 composite powders under this condition have high reactivity and uniform distribution.
Authors: Yuri I. Gordeev, Vitaly B. Yasinski, Aleksandr S. Binchurov, Nikolay E. Anistratenko, Irina V. Nikolaenko
Abstract: The results of experimental studies show that the use of composite powders (WC-Co) in combination with the modification by the additives of ceramic nanoparticles allows controlling the parameters of the microstructure and increasing the strength of the binder and the level of physical and mechanical properties of the hard metal in general. The coating of carbide particles with a layer of a binder is an effective starting method that allows to obtain a bulk compound that preserves the unique properties of the initial nanopowders and ensures a uniform distribution of the phases (WC, Co, Al2O3). Such multiphase fragmentary nanostructured composite is characterized by additional heterogeneity, determined by the differences in size and elastic properties of the phases. By combining the sizes and properties of the phase components in such heterogeneous composite, it is possible to increase the fracture energy (i.e. Palmqvist fracture toughness) up to 20 - 22 MPa∙m1/2 as a result of inhibition on inclusions of nanoparticles the stress relaxation and change in the trajectory of the intergranular crack. Based on the proposed stereological models and experimentally established relationships between composition and microstructure parameters, the required volume concentrations of nanoparticles’ additives and composite powders (WC-Co) were determined.
Authors: Ronyclei Raimundo Silva, Leonardo Resende, Rodolfo Albuquerque Buarque Assunção, Franciné Alves Costa, Uílame Umbelino Gomes
Abstract: The mechanical alloying of Mo-Cu powders allows the production of highly homogeneous sintered pieces, with very thin Mo particles and good dispersion of Mo particles in the ductile Cu phase, allowing the development of a route for the preparation of Mo-Cu simple composite powders, environmentally sustainable and able to increase the sinterability of the material without causing damage to their properties of thermal conductivity and electrical. Was used the precursor powders of molybdenum (Ammonium heptamolybdate) plus Cu, where two samples were prepared by mixing processes. For mechanical alloying, and by mixing manually, and both reduced and sintered in a resistive furnace with hydrogen gas. The materials were analyzed by optical microscopy, XRD and density measurements. The results confirm the effect of mechanical alloying on the increasing in high density of the sintered samples and thereby producing superior properties to those shown by the mixing manually sample.
Authors: Elena N. Korosteleva, Gennadii A. Pribytkov, Saltanat S. Kalambaeva, Victoria V. Korzhova, Vasiliy G. Durakov
Abstract: The paper presents the result of studies of composite powders produced by self-propagating high temperature synthesis (SHS) in the reaction mixtures of titanium, carbon and high chrome cast iron, and electron-beam coatings based on them. It was found that the morphology and dispersion of titanium carbide particles in the SHS-product were determined by cast iron powder content in the reaction mixtures. The effect of content of the SHS powders on the characteristics of electron-beam coatings, including abrasive wear resistance of facing coatings was shown.
Authors: Elena N. Korosteleva, Gennadii A. Pribytkov, Maxim G. Krinitcyn, Anton V. Baranovskii, Victoria V. Korzhova, Vladimir E. Strelnitskij
Abstract: The phase composition, microstructure and morphology of composite powders «TiC-HSS steel binder» obtained by the SHS method in layerwise combustion mode have been studied. Titanium powder, carbon (carbon black) in a ratio corresponding to equiatomic titanium carbide and high speed steel as a thermally inert binder was used as a reaction mixture. It was found that the mass transfer of reaction mixture components between the carbide and metal binder was taking place during synthesis, as a result of which the final phase and elemental composition of the synthesis products was formed. It is shown that the volume content of thermally inert binder significantly affects the dispersion of the formed carbide phase.
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