Vol.3 No.4 2011

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Research paper : New material development by the integration of cast technology and powder metallurgy technology (K. Kobayashi et al.)−293−Synthesiology - English edition Vol.3 No.4 (2011) developed in the stage from Type 2 Basic Research to product realization.4 From Type 2 Basic Research to product realizationFor the newly developed WC-FeAl hard material to be adopted widely as a practical material, it was important to find companies that would manufacture this material on an industrial scale. Even if the new material could be manufactured with the new process and showed excellent properties, no company that wished to engage seriously in this material could be found. However, as we have been presenting our information about the new hard material at academic conferences (the Japan Society of Powder and Powder Metallurgy) and elsewhere, industries were interested from the initial stages of the research. Therefore, to promote the practical use of the new material, we decided to collect experimental data deemed necessary by the companies by suggesting the products for which the material could be used. We positioned this stage as the Type 2 Basic Research that was difficult to carry out at universities or companies owing to the high-risks involved. We utilized the AIST “High-Tech Manufacturing” project and carefully scanned the keywords for using the WC-FeAl as a mold. The technological topics for realization were: (1) fabrication of large sintered compact for a practical mold, (2) a finishing process by conventional machining technology to determine the machining cost of the WC-FeAl hard material, and (3) resistance to thermal shock by heating-cooling, assuming the use of the mold in high temperature. Since some of the problems could not be addressed in our laboratory setting, we sought cooperation from universities and companies.In the fabrication of the large sintered body, as the pressure forming using the molten Al was used in the developed process, we found that molten Al functioned as the forming additive and the densification of the sintered body could be achieved with relative ease. By using high-voltage sintering equipment of greater capacity and applied pressure than that available at AIST, a large sintered compact with the same function as that achieved in the basic research was fabricated. The obtained large sintered compact is shown in Fig. 2. Its size (140 mm) would allow its use as a small mold. In the finish of the cemented carbide product, electro arc machining and wire cutting were used. These processes took advantage of the high conductivity of cemented carbide. Since the developed WC-FeAl sintered compact had high conductivity similar to conventional cemented carbides, wire cutting and electro arc machining could be used under the same machining conditions. In the wire cutting process of conventional cemented carbide, the machined surface reacted slightly and became discolored. However, there was little reaction in the case of WC-FeAl hard material owing to the good acid resistance properties of the FeAl phase. The WC-FeAl hard material sintered at AIST was processed into a mold (for small gear manufacture) at a machining company, and the appearance of the finish was the same as that obtained with a cemented carbide mold, as shown in Fig. 3. The time required for machining was about the same as the conventional cemented carbide. It was also confirmed that the new hard material could be processed at similar cost to the conventional cemented carbide. If this mold could be used for high-temperature forging, the processed material could be heated and then formed at high speed with a small forming load at high temperature, and the energy required for the process could be reduced. In general high-temperature forging, the molds are sometimes water-cooled. Therefore, we performed an experiment in which cemented carbide was heated to 900 ºC in air and then quenched in water. The appearance of the rapidly cooled samples is shown in Fig. 4. In the conventional cemented carbide, oxidation progressed rapidly, an oxide layer formed on the surface of the sample heated in the air producing a blue color, and cracks were produced due to heat stress when cooled rapidly. On the other hand, while the WC-FeAl hard material became slightly reddish-brown due to the thin oxide layer on the surface, it did not produce cracks. The developed WC-FeAl hard material did not readily oxidize when heated in the air, produced few cracks when water-Fig. 2 Photograph of a large-size WC-FeAl sintered bodyFig. 3 Photograph of the mold made using WC-FeAl

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