Papers by Keyword: Sintering Behaviour

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Authors: Hiroshi Fukushima, Masanobu Azuma, Yukihiro Kanechika
Abstract: A high temperature HRTEM holder equipped with a W-coil heater was used to make insitu observation of high temperature behavior of Al2O3 very thin (about 1 nm in thickness) protective film on AlN particles. The film was used to prevent AlN particles from damages by moisture. Rapid melting and rapid solidification of very small Al2O3 particles of about 2 nm in diameter were found within about 0.2 seconds. Therefore we concluded that the Al2O3 protective film worked as the sintering additives in the high temperature heating process. In the present study, very small Al2O3 particles were identified by the space between observed lattice fringe images. It was found that a tilt boundary was instantaneously formed and annihilated in an Al2O3 particle. There was also evidence that showed the formation and annihilation of edge dislocations within seven seconds during sintering.
Authors: Kenichi Takagi, Yuji Yamasaki, Koro Hirata
Abstract: The effects of V substitution for Cr to the sintering behavior of Cr containing Mo2NiB2 ternary boride base cermets and Mn addition to the mechanical properties and microstructure of the Cr and V containing cermets were investigated by using Ni-5.0B-51.0Mo-(17.5-x)Cr-xV (mass%) and Ni-5.0B-51.0Mo-12.5Cr-5.0V-(0-1.5)Mn (mass%) model cermets. 10mass%V substitution for Cr in the Cr containing cermets markedly improved transverse rupture strength and hardness from 2.27 to 2.94GPa and from 85.3 to 87.2RA respectively and refined the microstructure by retarding the progress of sintering especially at liquid phase sintering stage. Small amount of Mn addition to the Cr and V containing Mo2NiB2 base cermets significantly improved the sinterability and increased the mechanical properties of the cermets.
Authors: Christian Gierl-Mayer, Herbert Danninger
Abstract: The production of ferrous powder metallurgical parts by the press-and-sinter route becomes more and more attractive. Today, parts are produced for loading requirements that until now only could be fulfilled by conventional produced steel components. The high mechanical properties that must be attained require the use of alloying elements so far not common in powder metallurgy because of their high affinity for oxygen. The sintering of chromium containing steels is a challenge for the whole production process, because the reduction of the surface oxides is critical for successful sintering.Dilatometry can be a useful instrument to control the sintering behaviour of the materials, especially the combination with mass spectrometry allows analysing the very complex sintering process and simultaneously monitoring the solid-gas reactions. This work shows that the sintering atmosphere plays a major role in the entire process. Degassing and deoxidation processes during sintering are demonstrated for different alloying systems (Fe, Fe-C, Fe-Mo-C, Fe-Cr-Mo-C). Dilatometry coupled with MS is shown to be a very good instrument for process control of the sintering process. The generated analytical data can be related to the mechanical properties of the sintered steels if the size of the specimen is large enough.
Authors: T. Yamada, Y. Kanetsuki, K. Fueda, T. Takashashi, Y. Kohtoku, H. Asada
Authors: João M.G. Mascarenhas, Manuela Oliveira, C. Steven Wright
Abstract: This paper presents the results of an investigation into the sintering behaviour of three vanadium enriched variants of T42 high-speed steel. Powders were prepared by water atomization with vanadium and carbon contents of 6-8 wt% and 2.2 -2.7 wt%, respectively. These were annealed, die pressed and sintered in vacuum. All three alloys were sintered to full density giving “as –sintered” microstructures comprising globular MC carbides dispersed in a martensitic matrix. Optimum sintering temperatures were in the range 1240 - 1250°C with lower optimum temperatures associated with higher carbon levels. Sintering characteristics are correlated with phase diagrams calculated using ThermoCalc™ software and TCFe2000 database. The implications for the design of sinterable vanadium containing high-speed steels are discussed.
Authors: Atsushi Nakahira, K. Shiba, S. Yamaguchi, K. Kijima
Authors: Yu Xia Cao, Ling Zhong Du, Wei Gang Zhang
Abstract: CaB2O4 was added into hexagonal boron nitride (hBN) to improve the sintering behaviors of hBN. CaB2O4 and hBN were mixed and then pressed into plates. The plates were sintered at 2000°C for 5h under a N2 ambience. The phase compositions with different CaB2O4 contents were examined with X-ray diffraction analysis. The fracture cross-sections of the hBN plates were investigated by SEM. The apparent density and Rockwell hardness were also measured. The results show that the hBN particles had a plate-like shape and the grain sizes of hBN increased with increasing CaB2O4 contents. The apparent density and Rockwell hardness decreased with increasing CaB2O4 contents. When the CaB2O4 content was 15(wt) %, the hBN has the average grain sizes of 3μm in diameter and 200nm in thickness, the apparent density of 1.06 g/cm3 and the Rockwell hardness of 3, respectively.
Authors: Diletta Sciti, Daniele Dalle Fabbriche, A. Bellosi
Authors: Xian Xian Liu, Zhao Qiang Zeng, Bo Jun Chen
Abstract: Nanosized yttria stabilized tetragonal zirconia powders were prepared by chemical co-precipitation. By adding certain amount of wax emulsion, we obtained green compacts with the relative density ranged from 47% to 60%. Then the green compacts were sintered in air at the temperature from 1350°C to 1550°C. It turned out that the 3Y-TZP compacts were nearly fully densified after sintering at 1350°C and the grain sizes were between 200 to 300 nm. This result suggested that the addition of wax emulsion could improve the wettability between powders, elevated the density of the green compacts so that the coordination number and the contact points between particles were increased. With more transfer passages, the sintering behavior is remarkably improved.
Authors: D. Şimşek, R. Çiftçioğlu, M. Güden, M. Çiftçioğlu, Ş. Harsa
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