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Volume 49, Issue 4
Displaying 1-15 of 15 articles from this issue
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Huifen Peng, Nobuya Machida, Toshihiko Shigematsu2002 Volume 49 Issue 4 Pages 249-253
Published: April 15, 2002
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSSilver ion-conducting materials were synthesized for the composition xAgI⋅(100-x) (0.6Ag2S⋅0.4SiS2) (mol%) (0≤x≤90) by use of high-energy ball-milling process. Ball milling more than 40h led to the formation of amorphous samples in the composition range of 0 to 65 mol% AgI. On the other hand, the ball-milled samples with AgI content more than 70 mol% composed of amorphous phase and γ-AgI crystalline phase. Silver ion conductivity of the amorphous samples exponentially increased with an increase in the AgI content, and activation energies for conduction correspondingly decreased. The ball-milled 65AgI⋅21Ag2S⋅14SiS2 (mol%) sample showed the highest silver ion conductivity of 2.7×100 Sm-1 at 298 K and the lowest activation energy of 20.5 kJmol-1 among the obtained amorphous samples.View full abstractDownload PDF (400K) -
[in Japanese]2002 Volume 49 Issue 4 Pages 256
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (97K) -
Kenji Nakahara, Shuichi Imasato, Shigeya Sakaguchi, Yasunori Hayashi2002 Volume 49 Issue 4 Pages 257-263
Published: April 15, 2002
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe corrosion mechanism of WC-Ni-Cr cemented carbides and TiC-Ti-Mo sintered hard alloys were studied through investigating their corrosion behavior by the electrochemical method such as immersion test and polarization test in various solutions. For WC-Ni-Cr cemented carbides, the corrosion was mainly caused by the dissolution of binder Ni phase in both neutral and acidic solutions, and by the dissolution of W from WC phase and binder Ni-phase in alkaline solution. From the polarization curves of WC-Ni-Cr cemented carbide, the corrosion rate was found to depend on the carbon and Cr3C2 content of the alloy because of the difference in both the ability of passive film formation and the W content in the binder Ni phase. For TiC-Ti-Mo sintered hard alloy, the corrosion was mainly caused by the dissolution of fl-Ti phase in every test solutions. In the TiC-Ti-Mo sintered hard alloy, the spontaneously passivated film adapting to each environment was formed, causing the alloy to show an excellent corrosion resistance in every test solutions. In addition, the corrosion rate of the TiC-Ti-Mo sintered hard alloy increased in 5%HNO3 solution because the chemical decomposition of TiC phase itself might be occurred.View full abstractDownload PDF (555K) -
Shuichi Imasato, Shigeya Sakaguchi, Taikou Okada, Yasunori Hayashi2002 Volume 49 Issue 4 Pages 264-269
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCemented carbides with nickel binder have been widely used as wear and corrosion resistant material because of its improved corrosion resistance. However, WC-Ni cemented carbides were occasionally corroded in the aqueous solution with high NaCl concentration such as sea water. In this study, the effects of carbon content and NaCl concentration on the corrosion resistance of WC-Ni-Cr3C2 cemented carbides were investigated by immersion test and electrochemical measurements in 0.03, 0.3, 3, 10%NaCl solutions.
Ni was the main dissolved element, and the corrosion rate of high carbon alloy was lager than that of the low carbon alloy. The amount of dissolved metals increased with increasing NaCl concentration. The dissolution of Cr was increased with increasing NaCl concentration too, but not depended on carbon content in the alloy. The corrosion resistance declined with the increasing NaCl concentration owing to the destruction of the passive film with dissolution of Cr. The corrosion resistance largely depended on the passive film formed in solution, therefore influenced by the composition of the binder phase. The stable corrosion resistance was obtained with low carbon content alloy.View full abstractDownload PDF (1994K) -
Nobuaki Asada, Yoshiharu Yamamoto, Tadashi Igarashi, Yoshihiko Doi, Ko ...2002 Volume 49 Issue 4 Pages 270-278
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have already succeeded in synthesizing new mono-carbonitrides W (C, N) and Mo(C, N) with 11-20at%N and 14-25at%N respectively by heating W+C and Mo+C mixed powder in high-pressure N2 gas of 10-160MPa at 1523-1673K. In this study, the synthesis of new (W, Mo)(C, N) powder was tried by heating W+Mo+C mixed elemental powder and W-Mo solid solution alloy+C mixed powder in such high-pressure-N2gas. (W, Mo)(C, N) with N content of 14-24at% could be synthesized at 25 -160MPa in case of (W-Mo)+C mixed powder (Metal/C atomic ratio is 1/1), while (W, Mo)(C, N) could not in case of W+Mo+C mixed elemental powder.View full abstractDownload PDF (2152K) -
Kazuhiko Tanaka, Koji Hayashi2002 Volume 49 Issue 4 Pages 279-283
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe synthesis of new mono-carbonitride powders of W and Mo, i.e., W(C, N) and Mo(C, N), have already been succeeded by authors by a normal-pressure method, i.e., heating metal powder in CH4+NH3 mixed gas of normal-pressure. In this study, the synthesis of mono-carbonitride of Cr in the same VIA group in the periodic table as W and Mo was attempted by the normal-pressure method. As the result, Cr(C, N) containing a small amount of Cr3C2 and Cr2N was obtained by heating of 1173 K-57.6ks. The nitrogen content (N/Cr)of Cr(C, N) in the product was estimated to be between about 40 and 60 at%. This value was considerably lower than 78-92 at% of pure Cr(C, N) synthesized by high-pressure method, i.e., heating metal+C mixed powder in N2 of 100-150MPa.View full abstractDownload PDF (1925K) -
Keizo Kobayashi, Akihiro Matsumoto, Kimihiro Ozaki, Toshiyuki Nishio2002 Volume 49 Issue 4 Pages 284-289
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHard metal, which uses Fe3Al intermetallic compound binder, is a new wear resistant material with high oxidation resistance. As the particle sizes of Fe3Al powder synthesized by mechanical alloying process of elementary Fe powder and Al powder were about 30μm, the dispersibility of WC particles was so poor that the mechanical properties of the sintered compact degraded.
WC-20mass%Fe3Al alloy powder was prepared by mechanical alloying for 72ks using Fe powder, Al powder and WC powder as starting materials. The synthesized MA powder was filled up in a graphite mold and sintered at 1423 K by a pulsed current sintering.
The prepared sintered compact consisted of WC and Fe3Al phases. This showed that Fe3Al was synthesized from Fe and Al with a self-propagating high temperature synthesis (SHS) during sintering. The compact showed transverse rupture strength of over 1.3 GPa on account of homogeneous dispersion of Fe3Al. However, it is necessary to decrease the micropores in order to make a dense compact for industrial application.View full abstractDownload PDF (5390K) -
Eiichi Sentoku, Mituru Kito, Tatuo Nakagawa2002 Volume 49 Issue 4 Pages 290-293
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe machined surface of cast iron changes by cutting conditions because the surface of work receives the severe plastic deformation in high-speed cutting. The purpose of this paper is to study the effects of cutting work conditions on surface roughness and friction coefficient of the cast iron (FC300). Experimental conditions were in the ranges of cutting speed 1.67-6.67m/s, feed 0.05-0.3mm/rev, rake angle -5°--35°, and the depth of cut was 0.10-0.15 mm. The experiments were carried out using CNC lath, and the friction coefficient was measured using strain gauge.
Surface roughness of work was measured, after cutting experiment.
The main results are follows (1) Good surface roughness was given by low feed and high cutting speed. (2) The machined surface becomes rugged at cutting speed of 1.67m/s. Good surface roughness was obtained at cutting speed of 6.67m/s, because the surface of work material caused plastic flow. (3) The best surface roughness was obtained at rake angle of -15°, and the lowest friction coefficient was obtained at rake angle of -20°. (4) The friction coefficient is high at the feed is 0.05 or 0.3mm/rev, and increases with higher cutting speed.View full abstractDownload PDF (3114K) -
Yutaka Yanaba, Koji Hayashi2002 Volume 49 Issue 4 Pages 294-298
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn the previous studies on the room temperature transverse-rupture strength or fracture stress (σm), fracture toughness (KIC: SEPB method) and fracture origin size (2α) of polycrystalline hard or brittle materials, we have semi-theoretically derived and experimentally verified two equations of σm=ψKICSmf1/2 and σd-1 =σ0-1+Kα1/2: Smf is the total fracture surface area of all fragments of one test piece, σd is the maximum external stress on the fracture origin, etc..
In this study, based on the above each equation, we newly developed two methods for approximately estimating the fracture stress (σm) of the fractured test piece of hard or brittle materials from its fragments, whose fracture load and kind of material are both unknown. Method I: On condition that all the fragments are available, σm can be approximately estimated by use of σm-Smf1/2 correlation lines with a parameter of KIC or equation σm =ψKICSmf1/2 and by measuring Smf and estimating KIC from the correlation line between KIC and KICHV (fracture toughness measured by IF method). Method II: On condition that the fragment including the fracture origin is available, σm can be approximately estimated by use of σd-1-α1/2 correlation lines with a parameter of KIC and by measuring 2α, etc., and by estimating KIC in the same way as in Method I.View full abstractDownload PDF (2068K) -
Satoshi Kinoshita, Masaki Kobayashi, Koji Hayashi2002 Volume 49 Issue 4 Pages 299-305
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have already reported that room temperature fracture toughness of our newly developed WC-Co base cemented carbide (alloy) having highly oriented plate-like triangular prismatic WC grains are larger than that of the conventional alloy at an identical hardness of alloy. In this study, high temperature mechanical properties such as transverse-rupture strength (TRS), creep-rupture time, etc., of the new alloy at 1273 K were clarified to be superior than those of the conventional alloy: TRS of the new alloy was higher by 10-20% and creep rupture time was longer by 50-100% than the conventional alloy. The cause for such superiority was attributed to the difficulty in the generation and propagation of stable cracks in the new alloy compared with in the conventional alloy, probably due to more rigid skeleton of WC which were generated and grown by the reaction of CoxWyCz with graphite.View full abstractDownload PDF (5616K) -
Kusuhiko Sakagami, Shinichi Kouno, Tsutomu Yamamoto2002 Volume 49 Issue 4 Pages 306-311
Published: April 15, 2002
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSCarbide tools applied for plastic deformation often reach a tool life due to bending fatigue under repeated stress at their use. Therefore, as it is very important to acquire knowledge on bending fatigue of carbide tool, the effects of HIP treatment and surface conditions on the bending fatigue characteristics of WC-12mass%Co alloys were mainly investigated. The results obtained were as follows: (1) The bending fatigue characteristics of HIP-treated alloys was improved at lower repeated cycle, compared with that of normal sintered alloy. The fracture origin observed after fatigue fracture was pore in normal sintered alloy, while it was coarse carbide or Cc pool with a step-shaped form in HIP-treated alloy. (2) The specimens with different surface roughness had almost same bending strength, but the fatigue strength decreased with decreasing surface roughness. The cause of this decrease was considered to be due to the decrease of the surface compressive residual stress. (3) The fatigue strength of PVD-coated alloy with TiN layer decreased at lower. repeated cycle and that of CVD-coated alloy remarkably decreased, compared with that of non-coated alloy. The cause of these decrease in the coated alloys were mainly discussed in relation to the residual stress of the substrate alloy and the coated layer and the adhesion between them.View full abstractDownload PDF (8090K) -
Yuji Yamasaki, Nari Nishi, Ken-ichi Takagi2002 Volume 49 Issue 4 Pages 312-317
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMo2NiB2 base hard alloy consists of a Mo2NiB2 type complex boride as a hard phase and a Ni base alloy as a binder phase. According to previous investigation, additions of Cr and V to the alloy changed the boride phase crystal structure from orthorhombic to tetragonal and resulted in a remarkable improvement of mechanical properties associated with microstructural refinement. Moreover, an addition of Mn turned out to be effective for further improvement of the mechanical properties in the V containing alloy. In this investigation, Ni-5B-xMo-12.5V-2.5Mn (mass%) model alloys with four levels of Mo contents corresponding to Mo/B atomic ratio ranging from 1.0 to 1.3 were prepared to study the effect of the Mo/B atomic ratio on the mechanical properties and microstructure. The results indicated that transverses rupture strength (TRS) increased with increasing Mo/B atomic ratio and showed a maximum value of 3.2GPa at Mo/B=1.2 and then decreased with increasing the atomic ratio. Hardness increased linearly from 86.8HRA to 90.8HRA with increasing Mo/B atomic ratio.View full abstractDownload PDF (3321K) -
Jun-ichi Matsushita, Akimichi Hojo2002 Volume 49 Issue 4 Pages 318-322
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe boride ceramics have been attracting considerable attention as one of the newest advanced ceramics. In particular, titanium diboride (TiB2) has various desirable properties, such as a high melting point (3253 K), high hardness (32 GPa), and moderate electrical conductivity (105S). One of its major disadvantages, however, is poor sinterability. In this study, the effect of sintering aids addition on the pressureless sintering process of TiB2 ceramics was investigated. The addition of both Cr and C or Cr3C2 as the sintering aids accelerated the densification of TiB2 significantly. Simultaneous addition of about 5 to 10 mass% Cr and C or Cr3C2 resulted in high density, high bending strength and high Vickers hardness. According to the X-ray diffraction data of TiB2 composites fired at 1173 to 2173 K showed that Cr and C or Cr3C2 reacted with TiB2 to form CrB and TiC during the sintering process. CrB and TiC were formed at the grain boundaries of TiB2. Also, the solid solution between TiB2 and sintering aids was recognized. The SEM micrograph observation supported that a liquid phase was significantly concerned in the sintering of TiB2. The fracture surface of TiB2 sintered body showed both transgranular and intergranular fracture mode. It is considered that the addition of both Cr and C or Cr3C2 was effective in promoting the bonding between grains and removing pores to achieve high density in the sintered body. Thus, a sintered body of TiB2 having increased density, high strength and high hardness can be obtained by the addition of Cr and C or Cr3C2 to TiB2.View full abstractDownload PDF (5216K) -
Yoshihiro Shoji, Masaru Yoshinaka, Ken Hirota, Osamu Yamaguchi2002 Volume 49 Issue 4 Pages 323-326
Published: April 15, 2002
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSCr2N, CrN and their mixtures with desired fractions were prepared by self-propagating high-temperature synthesis (SHS) under controlled nitrogen pressure and then followed by hot isostatic pressing at 1300°C and 196 MPa under argon gas. The combustion temperature increased with increasing nitrogen pressure. Single-phase Cr2N and CrN were formed at 1040° under 0.18 MPa N2 and 1730°C under 2 MPa N2, respectively. The mechanical properties of chromium nitride ceramics with relative density of 99.2% were examined; Vickers hardness Hv(CrN:11.2 GPa and Cr2N: 14.5 GPa) linearly increased with increasing fraction of Cr2N, whereas fracture toughness KIC (-4.7 MPa⋅m1/2) and bending strength σb (-355 MPa) were constant regardless of the fraction of Cr2N/CrN.View full abstractDownload PDF (1706K) -
Hitoshi Sumiya, Shinya Uesaka2002 Volume 49 Issue 4 Pages 327-332
Published: April 15, 2002
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMicrostructural features and some properties of high-purity polycrystalline cBN synthesized from hBN by the direct conversion method were investigated. A fine-grained (<0.5μm) and homogeneous high-purity polycrystalline cBN was obtained at 7.7GPa and 2200-2400°C. At lower pressure and lower temperature than these conditions, compressed hBN remained in the polycrystalline sintered body. Some cBN grains became larger rapidly at higher temperature above 2400°C, and inhomogeneous microstructure was formed. The fine-grained and homogeneous polycrystalline cBN had higher hardness and TRS, compared with the coarse-grained and inhomogeneous polycrystalline cBN. The thermal conductivity of the polycrystalline cBN increased with increasing grain size or synthesis temperature. The thermal conductivity of the fine-grained polycrystalline cBN, however, was 3 to 4 times higher than conventional cBN compacts containing binder materials. The fine-grained and homogeneous high-purity cBN is expected to have high potential in cutting tool applications because of its excellent mechanical and thermal properties.View full abstractDownload PDF (3881K)
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