Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 60, Issue 9
September
Displaying 1-7 of 7 articles from this issue
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Paper
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  • Spark Sintering Behaviors on Mixtures of Fe – B and Fe Powders with Low Cost and their Characteristics
    Kazuhiro MATSUGI, Kensho TOMIGAHARA, Yong Bum CHOI, Gen SASAKI, Hideak ...
    2013 Volume 60 Issue 9 Pages 379-386
    Published: September 15, 2013
    Released on J-STAGE: October 17, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.379
    JOURNAL OPEN ACCESS
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    Spark sintering behaviors on mixed powders of Fe – B and Fe with low cost were investigated to develop the hard materials as substitution of WC – Co alloys. The cheap powders with mean composition of Fe – 19.1 wt% B consisting of mixed phases of B, FeB, Fe2B and Fe were ball-milled for crushing the particles with 45 µm. The ball milled Fe – B powders with 10 µm were 0, 10 and 50 vol% Fe added (hereafter called, 100, 90 and 50FeB, respectively). The spark sintering technique was utilized to fabricate ubiquitously hard-materials compacts. The promising maximum temperatures in sintering were defined on three compacts on the basis of the optimization of their Rockwell hardness and relative density. Rockwell hardness number on C scale was changed 66 to 71 depending on Fe contents on three compacts with the densities of 92 − 97 %, and the value of 100FeB compact was the same as that of WC – 7.8Co. The 100, 90 and 50FeB compacts showed the fracture strain of 0.32, 0.43 and 0.53 %, or fracture stress of 345, 435 and 447 MPa, respectively, in three points bending tests at 293 K. The fracture stress and strain were 5 − 17 % decreased and 7 − 9 % increased, respectively, on three points bended samples at 773 K, compared with those at 293 K.
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  • Improvement of Fatigue Properties of Ni Based René95 Superalloy by Metal Injection Molding
    Toshiko OSADA, Shunsuke MORINAKA, Yang XU, Fujio TSUMORI, Hideshi MIUR ...
    2013 Volume 60 Issue 9 Pages 387-392
    Published: September 15, 2013
    Released on J-STAGE: October 17, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.387
    JOURNAL OPEN ACCESS
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    Superalloys are widely used in gas-turbine components of aircrafts and power generating plants, and many other parts which need high temperature strength. However, there are issues to be overcome in conventional manufacturing methods; poor material yield and high processing cost. Metal injection molding (MIM) is expected to realize more complex near-net-shaping technique with significant cost savings. In our previous studies, MIM process was applied to Ni – based superalloy of René 95. By optimizing the process conditions, higher than 99 % of relative density was obtained and their tensile strengths at room and high temperature showed almost the same as those of wrought Inconel718. However, their dynamic properties at room temperature showed quite low level. The objective of this work is to improve the dynamic properties of René95 fabricated by MIM process. The effects of grain size, precipitated phase and remained pores on the properties were investigated. Finally, the fatigue strength of 443 MPa was obtained, which was almost as same as that of heat treated wrought Inconel718.
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  • Oxide-Ion Conduction Property of La1+xSr1-xGa3O7+δ Synthesized by Solution Method
    Naoto KITAMURA, Yusuke KUMAGAI, Yasushi IDEMOTO
    2013 Volume 60 Issue 9 Pages 393-396
    Published: September 15, 2013
    Released on J-STAGE: October 17, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.393
    JOURNAL OPEN ACCESS
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    LaSrGa3O7 – based oxide-ionic conductors were prepared by a novel solution method as well as a conventional solid-state method. From X-ray diffraction patterns, it was confirmed that La1.5Sr0.5Ga3O7+δ as well as LaSrGa3O7 were successfully prepared as a single phase of the melilite structure by both the synthetic processes. In addition, it was found that the grain sizes were 2～10 µm and a few hundred nm in the sintered samples synthesized by the solid-state and solution methods, respectively. As for these compacts, conductivity measurements were carried out with an AC impedance technique. As a result, it was demonstrated that the electrical conductivity was essentially independent of the synthetic method, even though the sintering temperature in the solution method was much lower than that in the conventional method. From the conductivity measurements under O2 and Ar atmospheres, it was also confirmed that La1.5Sr0.5Ga3O7+δ exhibited predominant oxide-ion conduction regardless of the synthetic method.
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Memorial Lecture of JSPM Award
  • Microstructural Control and Mechanical Properties of Advanced Ceramics
    Tatsuki OHJI
    2013 Volume 60 Issue 9 Pages 397-406
    Published: September 15, 2013
    Released on J-STAGE: October 17, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.397
    JOURNAL OPEN ACCESS
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    The mechanical properties of ceramics have been tremendously improved through well-organized control of the microstructure elements during the past few decades. This paper intends to describe how mechanical properties change via such microstructural controls, taking several examples of such research efforts in silicon nitride, one of the most important engineering ceramics. These include (1) super strong silicon nitride with > 2 GPa strength via refinement and alignment of fibrous grains, (2) super heat resistant silicon nitride with strength retention up to 1500 ˚C and toughness of ～800 J/m2 (double that of cast iron) via alignment of fibrous grains and adjustment of grain boundary phases, (3) porous silicon nitride via control of grain morphologies, and (4) porous silicon nitride with high strength (> 1 GPa), and high toughness (300 − 500 J/m2; far higher than that of the dense) via alignment of fibrous grains and pores.
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