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Volume 59, Issue 8
August
Displaying 1-13 of 13 articles from this issue
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Paper
Rapid Communication
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Kiyoshi Mizuuchi, Kanryu Inoue, Yasuyuki Agari, Masami Sugioka, Motohi ...2012 Volume 59 Issue 8 Pages 437-442
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSDiamond-particle-dispersed-aluminum (Al) matrix composites were fabricated in a solid-liquid co-existent state by Spark Plasma Sintering (SPS) process from the mixture of diamond powders, Al powders and Al-5mass%Si powders. As the diamond powders, two kinds of powders, monomodal diamond powders of 310 μm in diameter and a bimodal diamond powder mixture of 310 μm and 34.8 μm in diameter, were used. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were all well consolidated by heating in a temperature range between 798 K and 876 K for 1.56 ks during the SPS process. No reaction at the interface between the diamond particle and the Al matrix was observed by scanning electron microscopy for the composites fabricated under the sintering conditions employed in the present study. Although the relative packing density of the monomodal composite decreased from 99.1 % to 87.4 % with increasing the diamond volume fraction in a diamond volume fraction range between 50 % and 60 %, that of the bimodal composite was higher than 99 % in a diamond volume fraction range up to 65 %. The thermal conductivity of the bimodal composite was 455-581 W/mK, which is higher than that of the monomodal composite in a diamond volume fraction range higher than 60 %, and it is 530-581 W/mK in a diamond volume fraction range between 60 and 70 vol%.View full abstractDownload PDF (1013K)
Paper
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Masayuki Ohshima, Mamoru Daio, Mei Fusa, Toshimitsu Tetsui, Kazuhiro H ...2012 Volume 59 Issue 8 Pages 443-447
Published: July 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSMo/Nb/γ-TiAl functionally graded materials (FGMs) were prepared using a spark plasma sintering (SPS) method, and the MoSi2/Mo/Nb/γ-TiAl FGMs were then siliconized in molten salts. The MoSi2/Mo/Nb/γ-TiAl FGMs before and after oxidation at 1323 K in air were evaluated using optical microcopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The Mo/Nb/γ-TiAl FGMs were obtained by joining at 1373 K for 5 min using SPS. The Nb foil was firmly joined to the γ-TiAl surface and the Mo foil was firmly joined to the Nb foil. The ΔαNb-MoΔT and Δαγ-TiAl-MoΔT values were consistent with the criterion for stable FGMs without interlayer cracking of ΔαΔT less than 4.3×10-3, where ΔαNb-Mo and Δαγ-TiAl-Mo are the differences between the coefficients of thermal expansions of Nb and Mo, and between those of γ-TiAl and Nb, and ΔT is the difference between the SPS temperature and room temperature. The Mo/Nb/γ-TiAl FGMs were siliconized by dipping in a molten-salts mixture before heating in a mullite crucible at 1173 K for 40 h. The MoSi2Mo/Nb/γ-TiAl FGMs were dense and had neither cracks nor voids. The thickness of the MoSi2 layer was approximately 50 μm. The thickness loss of the MoSi2/Mo/Nb/γ-TiAl FGMs was 11 μm after the 200 h exposure to air at 1323 K. The thickness loss of the MoSi2/Mo/Nb/γ-TiAl FGMs was approximately 20 % less than that of NbSi2/Nb/γ-TiAl FGMs.View full abstractDownload PDF (1640K)
Special Issue: New Development of Hard Material and Coating Technologies
Summarization
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Hideaki Matsubara2012 Volume 59 Issue 8 Pages 450-
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSDownload PDF (128K)
Memorial Lecture of JSPM Award
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Yoshiharu Yamamoto2012 Volume 59 Issue 8 Pages 451-458
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSHard metal which is high performance in hardness and toughness is used as tool materials for high precision processing. Property of hard metal is improved to high hardness and high strength by refinement of WC phase. The further property improvement by refinement of WC phase is expected to tool materials such as micro drill, end mill, ultraprecision die.
The technology of obtaining finer WC powder for micro-grained hard metal by the direct carburization process in which WO3 powder is directly reacted with carbon powder and the inhibitors addition technology in which very fine primary crystals are formed into coarse polycrystalline WC grain by addition of grain growth inhibitor are investigated.
For the direct carburization process, very fine nuclei are formed at reduction step during WO2.72→WO2→W, and the fine nuclei is carburized to WC powder of nano sized from ultrafine grain diameter without grain growth. It was found out that hard metal obtained from the WC powder by the direct carburization process have higher hardness and strength. For the inhibitors addition technology, addition of grain growth inhibitors such as VC, TaC, Cr3C2, NbC, Mo2C at carburization process of coarse tungsten powder was examined. The very fine primary WC crystal are formed by adding Cr into coarse polycrystalline grain at carburizing process. Since Co diffuse into grain boundaries of the polycrystalline WC grain during sintering of hard metal, property of the hard metal was dependent on size of the primary crystal of WC powder. The Cr added WC powder can be contributed to stable production of micro-grined hard metal due to higher apparent density and lower oxygen content of WC powder.View full abstractDownload PDF (1148K) -
Hitoshi Taimatsu, Shigeaki Sugiyama2012 Volume 59 Issue 8 Pages 459-464
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSThis paper reviews our investigations for developing new types of binderless cemented carbides, WC-SiC ceramics. We first found that WC-SiC whisker powder mixtures were consolidated by using a resistance-heated hot pressing at a much lower temperature than pure WC powder. Eventually, regardless of whether SiC was added to WC powder in the form of whisker or powder, SiC addition was very effective for the densification of WC powder. Simultaneously the SiC addition vigorously grew WC grains and resulted in lowering the hardness of ceramics. This problem was overcome by the addition of a small amount of Cr3C2 or V8C7 widely known as a inhibitor of WC grain growth in WC-Co cemented carbides. Finally, for WC-10 mol% SiC-0.7 mol% Cr3C2, almost fully dense ceramics were obtained by pressureless sintering at 1750°C.View full abstractDownload PDF (1018K)
Review
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Makoto Inoue, Satoshi Kawagishi, Yasuhito Hagihara, Tsutomu Tomiyoshi, ...2012 Volume 59 Issue 8 Pages 465-472
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSWe developed a new type of saw wire for slicing hard materials. Then we tried to slice 50.8mm diameter sapphire ingots into wafers by using this wire.
The surfaces of wires are composed of two layers. That is, in the first layer, electroless Ni-P alloy plated diamond abrasive grains were temporarily fixed on the brass coated piano wire by using solder. And in the second layer, Ni was electroplated for reinforcement of the first layer.
The curvature radii of filets formed between solder layer and diamond abrasive grains can be adjusted arbitrarily according to change the depth of solder layer. The stress concentration at finally Ni electroplated filets can be reduced according to the preliminary adjusted shapes of filets.
When cutting off sapphire ingots by using these saw wires, cutting surface properties, such as average thickness, maximum surface waviness (WT) and total thickness variation (TTV) of sapphire wafers were generally favorable. And when running velocities of saw wires were varied in the range from 600 m/min to 400 m/min, cutting surface properties of sapphire wafers at the lowest running velocity of 400 m/min was superior in these running velocities of saw wires.View full abstractDownload PDF (1501K)
Paper
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Kenta Nakajima, Wataru Koike, Takuya Fujima, Ai Momozawa, Ken-ichi Tak ...2012 Volume 59 Issue 8 Pages 473-478
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSMechanical and physical properties of Cr containing Mo2NiB2 ternary borides were studied for (Mo2-XNi1-XCr2X)B2 compositions. X is set to 0, 0.25, 0.50 and 0.75 corresponding to the mixing compositions about 0, 5, 10 and 15 mass%. Dense Mo2NiB2 ternary borides were formed from the powders of Mo, MoB, Ni and CrB by reaction boronizing sintering with transient liquid phase. As a result, crystal structure of Mo2NiB2 ternary boride changed from orthorhombic to tetragonal around at 15 mass% Cr. Cr containing Mo2NiB2 ternary borides, especially 10 and 15 mass% Cr added borides exhibit high hardness and high elastic modulus comparable to WC and TiC. Cr containing Mo2NiB2 ternary boride is suitable alternative materials to wear resistant hard materials such as WC.View full abstractDownload PDF (1797K) -
Chao Liu, Motoshi Komatsu, Akihiro Nino, Shigeaki Sugiyama, Hitoshi Ta ...2012 Volume 59 Issue 8 Pages 479-483
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSCeramics composed of (W, Mo)C were prepared by reaction sintering WC-Mo2C-C powder mixtures at 1700°C using resistance-heated hot-pressing in which the solid-state reaction (1-x)WC+x/2Mo2C+x/2C→W1-xMoxC (x=0.05-0.40) occurred. The ceramics were then annealed at 2000°C. The hot-pressed and annealed ceramics were characterized by density, microstructure, and mechanical properties. Unreacted Mo2C remained in the ceramics before annealing; after annealing, the ceramics with x<0.2 were composed of W1-xMoxC. The solid-solution phase in each grain was not compositionally homogeneous, being separated into two phases of W-rich and W-poor regions. For the ceramics with x<0.2, Young's modulus decreased a little with x, and the Vickers hardness was almost constant. The fracture toughness did not show a significant dependence on x.View full abstractDownload PDF (1001K) -
Chao Liu, Akihiro Nino, Shigeaki Sugiyama, Hitoshi Taimatsu2012 Volume 59 Issue 8 Pages 484-488
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSBinderless cemented carbides consisting of a (W, Mo)C solid solution and SiC were synthesized and consolidated by resistance-heated hot pressing of WC-Mo2C-C-SiC powder mixtures in the temperature range of 1600 to 1800°C. The microstructures and reaction products of the ceramics were examined, and their density and mechanical properties were measured. The solid-state reaction for synthesizing (W, Mo)C solid solutions is (1-x)WC+x/2Mo2C+x/2C→W1-xMoxC. Without the addition of SiC, Mo2C remained after hot pressing. However, for (W, Mo)C-SiC ceramics obtained from the powder mixtures with SiC content ≥ 5 mol% and x ≤ 0.2, very little residual Mo2C was observed. Each (W, Mo)C grain was composed of a W-rich core phase and a W-deficient phase on the core's periphery, suggesting a two-phase separation during cooling. The (W, Mo)C-SiC ceramics with x ≤ 0.2 were densely sintered, and their Young's modulus changed with the SiC content according to the Voigt mixture rule. The (W, Mo)C-SiC ceramics sintered at 1600°C had high hardness above 23 GPa and a fracture toughness of ∼5.8 MPa m1/2.View full abstractDownload PDF (1416K) -
Yukihiro Hosoda, Kusuhiko Sakagami, Toshiya Nakata, Tsutomu Yamamoto2012 Volume 59 Issue 8 Pages 489-493
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSWC-βt-Ti(C, N)-Co alloys have different microstructures near surface due to sintering atmosphere. In order to evaluate the characteristics of these alloys with sintered surface, the effects of Ar and N2 sintering atmosphere on the hardness near surface and turning performance of these alloys were investigated. The obtained results were as follows; (1) The thickness of extreme surface layer without βt was slightly larger in Ar than N2 sintering atmosphere. It was mostly consistent with the area proportion of WC phase. Moreover, the microstructure change of the alloy under Ar sintering atmosphere was rather remarkable judging from the result of EDS analysis. (2) The hardness near surface of the alloy was higher in Ar than N2 sintering atmosphere. It was considered to be mainly due to Co content near surface of the alloy. Consequently, (3) the alloy under Ar sintering atmosphere was superior in flank, nose and crater wear resistance as compared with the alloy under N2 sintering atmosphere. (4) The alloy under Ar sintering atmosphere showed better fracture resistance than the alloy under N2 sintering atmosphere.View full abstractDownload PDF (1512K) -
Hiroyuki Nakayama, Kimihiro Ozaki, Keizo Kobayashi2012 Volume 59 Issue 8 Pages 494-498
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSEffects of Al contents on a microstructure of TiB2-(Fe-Al) cermets prepared from a powder mixture of TiB2, Fe and Al were investigated. The contents of binder phases were Fe3Al, Fe3Al2 and FeAl used. The Al addition improved a relative density of the cermets compared with the non Al added TiB2-Fe cermets. This is because the molten Al infiltrated into the gaps between TiB2 particles during the sintering due to the good wettability of Al and TiB2, followed by the formation of (Fe-Al) phase occurred by a reaction between molten Al and solid Fe. The relative densities of the samples with Fe3Al2 and FeAl binder phase were lower than that of the sample with Fe3Al binder phase. An increase in Al content increases an order-disorder transition temperature of the (Fe-Al) phase; thus the sintering in the sample with Fe3Al2 and FeAl binder phase was carried out in the ordered state of the binder. The ordered phase usually shows a low deformability. Therefore, the sintering of the sample with Fe3Al2 or FeAl phases shows the lower relative densities than the sample with Fe3Al phase.View full abstractDownload PDF (1523K)
JSPM Announcements
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2012 Volume 59 Issue 8 Pages Pref8_1-
Published: August 15, 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSDownload PDF (81K) -
2012 Volume 59 Issue 8 Pages Mtg8_2-Mtg8_6
Published: 2012
Released on J-STAGE: November 30, 2012
JOURNAL OPEN ACCESSDownload PDF (250K)
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