Papers by Keyword: Powder

Abstract: The results of microanalysis of additive products from electro-erosive cobalt-chrome powders are presented. It has been established experimentally that the obtained samples of additive products from powders, obtained by electro-erosive dispersion of cobalt-chrome wastes in alcohol, have a microcrystalline structure with a porosity of less than 0,78%. The obtained experimental data can be used in the development of promising resource-saving technologies for the manufacture of machine parts.

Abstract: The main requirement for powders for additive 3d technologies is the spherical shape of the particles. Such particles are most compactly packed into a certain volume and ensure the "fluidity" of the powder composition in the supply systems of the material with minimal resistance. The wide use of the EED method for processing metal waste into powders for the purpose of their reuse and application in additive technologies is hampered by the lack in the scientific and technical literature of full-fledged information on the effect of the initial composition, regimes and media on the properties of powders and technologies of practical application. Therefore, in order to develop technologies for the reuse of electroerosive powders and to evaluate the effectiveness of their use, complex theoretical and experimental studies are required. The aim of the work was to conduct a phase analysis of additive products from electroerosive cobalt-chrome powders. The phase composition of the samples was studied by X-ray diffraction on a Rigaku Ultima IV diffractometer in Cu-Kα radiation (wavelength λ = 0.154178 nm) using Soller slits. Based on the results of the X-ray diffraction analysis of additive articles from electroerosion cobalt-chrome powders, it has been experimentally established that the main phases in the sintered samples are Co, Cr and Co₃C.

Abstract: The results of the research of the use of powders based on tungsten carbide with a particle size of 1 μm or less, obtained by the method of electro-erosion dispersion from the waste of sintered hard alloys, as a dispersed phase of composite galvanic coatings based on iron during the restoration and hardening of car parts are presented. It is shown that the introduction powders of hard alloys of grades VK8 and T15K6 in the chloride electrolyte of iron plating with a concentration of 100 g/l and more, practically does not affect the micro-hardness, but allows to increase the relative wear resistance of the obtained composite galvanic coatings, compared to simple iron galvanic coatings, and, at the same time, increase the life of parts and reduce repair costs.

Abstract: The influence of the concentration of the initial solution on the size and composition of the particles obtained by the method of ultrasonic spray pyrolysis (USP) was investigated. An aqueous solution of Fe (NО₃)₃·9Н₂О, the concentration of which varied in the range of 0,0025–0,03 mol/l, was used as the starting material. As a result of the process, iron oxide particles were obtained, the average size of which varied from 123 to 292 nm. Based on FTIR and XRD, powders consist of several phases and have crystalline inclusions α-Fe₂O₃, β-Fe₂O₃, and γ-Fe₂O₃.

Abstract: Titanium is a hard metal with good mechanical properties, corrosion resistant and biocompatibility which makes it have a wide range of applications (biomedical and aerospace). Severe plastic deformation (SPD) is employed to produce Ultrafine Grained (UFG) structures. UFG structures have better mechanical properties due to their compaction. Equal Channel Angular Pressing (ECAP) is adapted to produce a UFG structure in Titanium. In this process, titanium sponge powder is filled in the aluminium shell by intermediate tapping to fill the volume of the shell. The shell is then closed with an Al cap and ECAP is done with continuous back pressure at 300°C. The test specimen has undergone four passes in route B_C at different back pressure (50, 100 and 150 MPa) where titanium is consolidated without any crack. Titanium showed decreased grain size and porosity with increasing backpressure. In particular, it is seen that the sample ECAPed by 100 MPa backpressure showed a relative density of about 98% with a hardness of 37 HRC. It is seen that ECAP is more economical and the product obtained by the ECAP process has better properties.

Abstract: The aim of this research was to optimize the mechanically activated synthesis (MAS) technology of the Cr₃C₂-Ni powder intended for thermal spraying. The MAS production route included ball milling for 72 h (ball-to-powder ratio 20:1) and sintering under 1075 °C in vacuum for 4 h. Sintered compact was crushed, classified by sieving to obtain the fraction suitable for thermal spraying (20–45 μm). The morphology and the phase composition of the powder were analyzed by a scanning electron microscope (SEM) and X-ray diffraction (XRD). The optimal Cr:C ratio found was 7:1. The powder had an equiaxial or a slightly elongated lamellar shape, Cr₃C₂ carbides in a single powder particle had an elongated shape. The principal phases in the optimized powder were Cr₃C₂, Cr₇C₃ and Ni (Cr) solid solution. Coatings from the manufactured powder were produced by the high velocity oxy-fuel (HVOF) spraying. The abrasive wear tests were carried out according to standard ASTM G65. The wear tests showed that the sprayed coatings from the experimental powder exhibited about five times higher wear rate at abrasive wear conditions than the coatings from the reference commercial powder.

Abstract: The aim of this article is to develop a method in order to investigate the surface modifications of degraded polyacrylonitrile powders under microwave treatment in air. Microwave treatment of polyacrylonitrile powders in air recorded two stages of degradation firstly an exothermic reaction that started in the range of (86-117)°C. Secondly the Thermal runway here the weight loss reached a peak value between 80-90 percent with the small quantity of 0.25g polyacrylonitrile and in the ashes with a bigger quantity 1g of polyacrylonitrile. Scanning electron microscopy analysis technique revealed the morphological characteristics and the porosity of the carbon compound that may play an important role in the construction of high porosity area and so in electrochemical supercapacitor devices with high performances.

Abstract: Already, there are several processes to produce intermetalic alloy parts from powder , ex. metal injection molding (MIM) or additive manufacturing (AM). For these processes, pre-alloyed powder made by gas atomized powder is used because of their quality. As other way, intermetallic alloy can be produced combustion reaction process. On this process, ingredient metal powders are mixed and reacted by combustion. However, powders are fused by reaction heat, and they are difficult to keep the powder condition. There for, we are developed the process to produce intermetallic alloy precursor by slow combustion reaction. On this process, temperature of mixed powders increases slower than 0.2K/sec. while the combustion reaction, and powders are reacted without fusing. Using this process, TiAl presursor is synthesized. Relation of reacting condition and quality of the precursor is evaluated, and researched the practical usage of this precurser.

Abstract: In this study, LMD-CLAD® process (Direct Laser Additive manufacturing) is developed for alumina and Al₂O₃-Y₂O₃-ZrO₂ ternary eutectic compositions. Powder flowability, laser-material interaction and thermal gradient control have been investigated. Powder granules of aforementioned compositions have been designed by spray-drying. Particle size distribution, Hall funnel test and SEM observations have been performed. Flowability has been improved by 20% in order to match with the LMD-CLAD® process by adjusting their density, size and surface quality. Otherwise, optical absorption of the ceramics has been increased up to 90% thanks to the addition of doping ions. With such a flowability improvement, laser powder deposition tests were successful and enabled us to investigate the effect of laser parameters and thermal environment on deposited beads state.

Abstract: In this research, a composition optimized In718 superalloy powder suitable for additive manufacturing has been developed by using the vacuum induction melting gas atomization (VIGA) and the powder sieving process. VIGA which combines the vacuum induction melting (VIM) and gas atomization (GA) processes uses high pressure inert gas to atomize the metal melt formed by VIM to form metal droplets. These metal droplets are solidified to form metal powders during the falling process in the atomized chamber. After the sieving process, the mean particle size D₅₀ of the powder is less than 35 μm and the particle size distribution (PSD) ranges from 10 to 55 μm (D₁₀~D₉₀). Besides, the produced powder has high flowability (I_Carr ≦15), which is suitable for selective laser melting (SLM) additive manufacturing (AM). After the SLM process, the tensile tests are conducted at room temperature and high temperature of 650°C. The results show that the high temperature properties of the optimized In718 superalloy are superior to the commercial In718 superalloy.