Papers by Keyword: Isostatic Pressing

Abstract: Jet grading technology is an efficient process in different industries. In this research, tungsten powder with different particle size distribution was used as a raw material to produce tungsten products via isostatic pressing as well as sintering. The mechanism of jet grading and the morphology and particle size distribution of different precursors were analyzed. The results showed that jet grading technology had remarkable effect on tungsten powder classification. The appropriate grading treatment was helpful to the formation of tungsten products with high performance. After jet grading and the following process like pressing and sintering, the tungsten products with better properties were manufactured which was used fischer particle size of 3.0~3.5μm as the raw material. The obtained products’ density was 18.77g/cm³ and its hardness was 372.15HV_0.3.

Abstract: Composites are the combination of materials that are mixed together to achieve specific structural properties. Teflon (Polytetrafluoroethylene PTFE) consists of long-chain molecular structure. Its monomer consists of two carbon atoms each of them having flourine atoms attached. Bonds within each chain are strong covalent bonds where as the secondary bonds between two chains are weaker. By raising temperature, the distance between the chains increases providing good adjustment of the atoms of other materials due to anisotropy of its mechanical properties. Powder metallurgy technique using hot isostatic pressing, a hybrid densification process in which pressure and temperature are applied at the same time, has been used to develop a teflon-copper composite material. Three samples were prepared by changing the teflon-copper composition as 60:40%, 65:35% and 70:30% by weight. Commercially available powders of teflon and copper of grain size ~ 40 μm was used. The aim to develop this type of material was to increase its density (~ 4 g/cm³), and hardness. The commercial applications of such type of composite material are solid lubricants, sleeves, bearings etc. In this paper the effect of composition on hardness, tensile strength and surface roughness is studied.

Abstract: The paper assesses the effectiveness of uniaxial and cold isostatic consolidation methods of medium size ceramic granular press-powders. The results of fractographic studies of raw compacts were obtained with different methods of forming. The estimation of the physical properties of raw compacts and sintered ceramic samples was done. The results of measurement of the bending strength of the ceramic material are shown. It has been established that the application of isostatic forming, compared with axial allows increasing the flexural strength of the ceramic material is more than 35% due to creating denser structure and enhancing adhesion between the granules under otherwise equal technological conditions

Abstract: The flow behavior of a 7039 aluminum alloy and the corresponding microstructural evolution during hot deformation were studied by Gleeble-1500 thermal simulation tests, EBSD and TEM observations with temperatures ranging from 300 °C to 500 °C under strain rates from 0.01 s^-1 to 10 s^-1. It has been shown that the flow stress increases with the decrease in the deformation temperature and increase in the strain rate. The degree of dynamic recrystallization (DRX) increases with the increase in the deformation temperature and strain rate in 7039 aluminum alloy. The complete dynamic recrystallization occurs at 500 °C with a strain rate of 10 s^-1.

Abstract: New powder compaction process, in which a Bingham semi-solid/fluid mold is utilized, is developed to fabricate micro parts. In the present process, a powder material is filled as slurry in a solid wax mold, dried and compressed by either of conventional pressing methods, such as isostatic pressing or die compaction. It is important to use slurry for filling because dry powder is hard to fill in the micro cavity. It is also essential to control process temperature to treat micro parts. The wax mold is heated during compaction and becomes semi-solid state, which can acts as a pressurized medium for isostatic compaction. Since the compacted micro parts are very fragile, the mold's temperature is controlled to higher than its melting point during unloading, to avoid breakage of the compacts. To demonstrate effectiveness of this process, some micro compacts of alumina are shown as examples.

Abstract: Submerged Entry Nozzle (SEN) are usually made from a combination of carbon bonded alumina, zirconia and magnesia with graphite, which have been found to give the best response to the extreme demands of thermal shock, corrosion and erosion resistance. SEN brittle fracturing and clogging is a serious productivity and quality problem in continuous casting. The SEN critical area of failure is the steel flange where the SEN neck is fixed. Thermal shock or mechanical stress may cause cracking, which can result in premature failure. Preheating on optimal temperature before SEN installation is the standard procedure. Thermal stress effect on fracture behavior was done by analyze of material fractography, morphology, macrostructure and microstructure.