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 63, Issue 1
January
Displaying 1-8 of 8 articles from this issue
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Paper
Memorial Lecture of JSPM Award
  • Numerical Methods for Controlling Shape, Size and Microstructure of Sintered Compacts
    Kazunari SHINAGAWA
    2016 Volume 63 Issue 1 Pages 3-9
    Published: January 15, 2016
    Released on J-STAGE: February 11, 2016
    DOIhttps://doi.org/10.2497/jjspm.63.3
    JOURNAL OPEN ACCESS
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    Predictions of the shrinkage behavior and the microstructural evolution of powder compacts during sintering are important to control the shape, size, and properties of sintered parts. Three kinds of numerical methods for simulating the sintering process at particle level are reviewed, and their characteristics are compared. First, a repeated unit cell model used in the finite element analysis for sintering is introduced. By analyzing the diffusional creep due to the surface tension, various kinds of information about powder particles such as the distributions of stresses and strain rates can be obtained. Secondly, phase-field modeling of microstructural evaluation in sintering process is presented for mesoscale simulation. Anisotropic abnormal grain growth at the later stage of sintering is demonstrated by considering the change in interfacial energy and mobility. Phase-field simulation of grain growth behavior in polycrystalline powder is also conducted. However, it is difficult to compute the sintering shrinkage in the phase-field approach by itself. Finally, a combined phase-field/discrete-element method is proposed to treat both grain boundary migration and sintering shrinkage, as a useful tool for mesoscale simulation.
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Paper
  • Effect of Building Position on Phase Distribution in Co-Cr-Mo Alloy Additive Manufactured by EBM
    Taiyo TAKASHIMA, Yuichiro KOIZUMI, Yunping LI, Kenta YAMANAKA, Tsuyosh ...
    2016 Volume 63 Issue 1 Pages 10-16
    Published: January 15, 2016
    Released on J-STAGE: February 11, 2016
    DOIhttps://doi.org/10.2497/jjspm.63.10
    JOURNAL OPEN ACCESS
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    Co-Cr-Mo alloy is used for biomedical implant such as artificial joint because it has excellent wear and corrosion resistances and biocompatibility. Electron beam melting (EBM) is a type of additive manufacturing technology for metals. We fabricated 20 rods of Co-Cr-Mo alloy with height of 160 mm arranged in a 4 × 5 matrix and observed phase constitution at the middle part (80 mm in height) of the rods by SEM-EBSD. We found that the rods in the center part of the matrix had more γ-fcc phase and less ε-hcp phase than those in the outer part. This difference in the phase fraction occurred probably because the rods surrounded by other rods were held at higher temperature due to the inhibition of thermal dissipation to the surroundings. We should take into consideration this difference in the thermal history when we fabricate many objects simultaneously.
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  • Bending Durability of Ni-Mo pre-alloyed Sintered Steel Case-Carburizing Gears with Different Densities and Tooth Root Bending Stress Analysis Using FEM Model Considering Voids
    Takahiro NAGATA, Teruie TAKEMASU, Takao KOIDE, Satoshi NISHIDA
    2016 Volume 63 Issue 1 Pages 17-22
    Published: January 15, 2016
    Released on J-STAGE: February 11, 2016
    DOIhttps://doi.org/10.2497/jjspm.63.17
    JOURNAL OPEN ACCESS
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    Single tooth bending fatigue tests were first carried out using Ni-Mo pre-alloyed sintered steel (46F4H) spur gears with different densities in the range of 7.30~7.54 Mg/m3. The sintered gears specimens were machined from sintered steel packs made from the single-press single-sinter route and some were surface-rolled using CNC form rolling machine. All test gears were case-carburized. The experimental results showed that the surface-rolled sintered gears with a density of 7.40 Mg/m3 or more had sufficiently high bending fatigue strength to replace gears made of typical Cr-Mo case-carburized wrought steel. Then, the stress analysis in the root fillet area of gear teeth was performed using a FEM simulation model considering a void distribution. The peak value of the maximum principal stress in the surface near the most critical stressed point was increased with the increase of porosity for un-surface rolled gears and was decreased as the amount of surface fully densified depth was increased. These simulation results can explain well the experimental results and show the appropriate material initial density and the surface densification level.
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  • Oxidation and Corrosion Resistance of Molybdenum-Chromium Nitride Sintered Compacts
    Masahiro NAGAE, Naoko ISE
    2016 Volume 63 Issue 1 Pages 23-28
    Published: January 15, 2016
    Released on J-STAGE: February 11, 2016
    DOIhttps://doi.org/10.2497/jjspm.63.23
    JOURNAL OPEN ACCESS
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    The oxidation characteristics in air were investigated for Mo-Cr nitrides prepared by pulsed electric current sintering (PECS) of mixed Mo2N and CrN powder, in addition to their corrosion characteristics in boiling sulfuric acid. Mo2N type solid solutions were found to be easily formed using PECS. Sintered compacts with a CrN content of >35 wt% consisted of two kinds of solid solution: Mo2N type with a Cr:Mo atomic ratio of about 1:1, and a Cr-rich phase. The solid solubility limit for Cr in Mo2N was about 50 at%. The hardness of the sintered compacts decreased with increasing CrN content, and their density increased. Although Mo2N (0 wt% CrN) was strongly oxidized at temperatures above 773 K, sintered compacts with a CrN content of >35 wt% were highly resistant to oxidation even at temperatures above 1073 K. All of the sintered compacts except that containing 100 wt% CrN exhibited perfect corrosion resistance in boiling sulfuric acid (75 wt%).
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