Authors: J. Abenojar, P. Díaz, M.A. Martinez, Francisco Velasco
304
Authors: Zhi Yu Xiao, Jun Wang, Shu Hua Luo, Li Pin Wen, Yuan Yuan Li
Abstract: Warm compacting and sintering behaviors of pre-mixed Fe-2Ni-2Cu-1Mo-1C powders
were studied. Results showed that green density increased with compacting temperature and then
fell slightly; the maximum green density was obtained at about 120°C. Green compact density and
spring back effect of the pre-mixed powder increased gradually as the compacting pressure
increased. Sintered density first increased and then fell as the temperatures went up under different
sintering temperatures for 50 minutes, but the trends of sintering dilatation were first reduced and
then increased. Sintered density first reduced and then increased with the prolonged sintering time
at 1300°C, but the trends of dimension change after sintering were the very reverse. Tensile strength,
elongation and hardness of the warm compacted Fe-2Ni-2Cu-1Mo-1C materials generally increased
as sintering temperature and sintering time went up.
1621
Authors: Abolfazl Babakhani, Ali Haerian
Abstract: In conventional warm compaction, both powder and die are heated to a certain temperature during compaction. This is a technique for producing P/M compacts with higher green and sintered strength as compared to room temperature pressing. However, there is a certain limit to powder temperature due to flow problems at higher temperatures. Heating the die above this practical limit can further improve properties. In this work, the effect of die temperature on green and sintered properties of Astaloy CrM powder has been investigated. Here, the powder at 135 oC was fed to the die at different temperatures. Density and strength for samples in green and sintered conditions were evaluated for two compaction pressures of 500 and 650MPa and temperatures ranging from ranging from 135 to 165 oC. Comparison of samples compressed at room temperature showed marked improvement in density and strength properties. A 22% increase in density, as well as 40% increase in green strength was observed. Tensile and impact strengths were improved by about 10% and 20% respectively. SEM micrographs showed more rounded pores and hence reduced stress raising sites. The improvement in properties can be mainly attributed to changes in powder morphology and die wall lubrication due to migration of hot lubricant from interparticle space to die walls. The latter will reduce particle spacing and bring about more intimate metal-metal contacts as well as better lubrication on die walls.
1802
Authors: Christian Ghermec, Olimpia Ghermec, Mario Trotea
Abstract: The elaboration of carbon steels sintered through the enrichment of compactised iron powders in carbon in methane gas medium has allowed the development of an innovative technology that fort he first time is based upon the carburizing (the process of carbon enrichment, in different proportions) at the same time with sintering. The parts obtained through this proceeding have been analysed from the point of view of the physical and the mechanical characteristic in correlation with the compaction pressure of the iron powder.
113
Authors: Mohammed A. Almomani, Ahmad M. Shatnawi, Mohammed K. Alrashdan
Abstract: In this paper, several copper matrixes reinforced with 1 wt. % silicon carbide (SiC) were fabricated using powder metallurgy (PM). The effect of sintering time (30 min, 60 min, 90 min, and 180 min) on composite density and porosity, and grain size were investigated. The results showed that longer sintering time gives higher sintered density, and smaller porosity content. This is due to the diffusion enhancement, which leads to reduce pore size, and close porosities. Also, for a given compaction pressure, the grains tend to be coarser for longer sintering time, due to the materials tendency to reduce grain boundary surface energy. In addition, samples compacted at high pressure have finer grain than corresponding grains compacted at low pressure but sintered for the same time.
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