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Volume 45, Issue 6
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[in Japanese]1998 Volume 45 Issue 6 Pages 498
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (118K) -
Toshiyuki Takahashi1998 Volume 45 Issue 6 Pages 499-506
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSAl2O3 based ceramics is considered to be useful for high speed cutting of steel and low machinability material because of its higher chemical and thermal stabilities than those of coated cemented carbides or cermets. However, it has many problems to be solved in the mechanical properties which is necessary for the cutting tool.
This study is concerned with the improvements of mechanical properties and cutting performance of the Al2O3 ceramics. After the cutting performance of Al2O3-TiC ceramic tools having 10-50mass%TiC and various grain size was investigated, the strengthening of TiC-free white ceramics which has excellent wear resistance in high speed cutting was studied. The flank wear in the turning test of gray cast iron decreased with decreasing TiC content and increasing TiC grain size. The tool having 20-30mass%TiC and finer TiC grain size showed a superior resistance to flaking and flank wear in the turning test of alloy tool steel. The room temperature transverse-rupture strength of the fine grained white ceramics reached about 1.3GPa in contrast to 0.7-0.9GPa of conventional one.View full abstractDownload PDF (8148K) -
Ken-ichi Takagi1998 Volume 45 Issue 6 Pages 507-514
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSBorides are promising candidates for wear resistant materials. But poor sinterability and extreme brittleness of borides retarded the fabrication of bulk materials. This paper gives criteria for the development of boride base cermets. Reaction boronizing sintering developed by us is a novel strategy to form a ternary boride coexisting with a binder metal during sintering associated with liquid phase formation. This new sintering technique has successfully brought development of three ternary boride base cermets such as Mo2FeB2, Mo2NiB2 and WCoB base ones. This paper describes the sintering behavior, mechanical properties, microstructure and phase formation related with the alloying elements on Mo2NiB2 boride base cermets. This paper also illustrates Reitveld analysis results of the complex boride structure in the cermets.View full abstractDownload PDF (6787K) -
Masaya Miyake1998 Volume 45 Issue 6 Pages 515-522
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDue to its superior resistance to thermal shock, wear and oxidation, and high toughness, Si3N4 ceramics are expected to be used in industrial applications. However, before these Si3N4 ceramics can become better established on the market, their fracture strength, fracture toughness characteristics and reliabilty must be improved.
In this study, the formation mechanisms of the inside pores at the pressureless sintering conditions that yield the thick body of uniform structure were invesigated.
The creep properties of sintered body were studied by analyzing the results of internal friction measurements.
Hugoniot-compression curve for Si3N4 ceramics with controlled microstructure were measured to study the yeilding properties under shock compression. And the correlations with Hugoniot-elastic limits and microstructure of Si3N4 ceramics were considered.
The degradation characteristics of bending strength of specimens after processing under various grindingg condition were evaluated.View full abstractDownload PDF (5924K) -
Yutaka Yanaba, Koji Hayashi1998 Volume 45 Issue 6 Pages 523-528
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe tedious manual procedures and long time needed for the measuring of Smf which is the main process in our proposed method for estimating fracture toughness (KIC) of hard materials by using our proposed equation ofσm=ψKICSmf1/2(σm is the bending fracture strength, ψ is a factor and Smf is the macroscopic fracture surface area of all fragments of one test piece) were tried to avoid and shorten respectively by automating the main procedures.
The results were as follows: (1) The procedures which were successfully automated, and the devise or software used for the automation were as follows, respectively: (1-1) The moving of the fragment at a regular interval to the direction of X- and Y-axes in order to hit the laser beam of displacement meter onto a lot of measuring lattice points imaginarily figured on the fracture surface, and the use of automatic X-Y mechanical stage, (1-2) The inputting of data on Z-coordinates of all lattice points obtained by laser displacement meter to personal computer, and the uses of PC card and data collection software which converts analog data on Z-coordinates from the displacement meter to digital ones appropriate to the input, and orders the input of the data to the computation program, respectively. The calculation of Smf from these coordinates was of course instantaneously made by using the computation program including X-and Y-coordinates, in a similar way as in the previous method. (2) The measuring time of Smf for WC-10mass%Co cemented carbide was shortened by the automations to be about 24% of the one needed in the previous manual method.View full abstractDownload PDF (528K) -
Yutaka Yanaba, Koji Hayashi1998 Volume 45 Issue 6 Pages 529-534
Published: June 15, 1998
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSIn order to clarify whether our theoretically derived equation of σm=ΨKicSmf1/2(σm; three-points bending fracture strength, Ψ shape factor, KIC; fracture toughness, Smf; total macroscopic area of fracture surface) can be applied to brittle materials having considerably lower KIC and σm than those of WC-10mass%Co cemented carbide, etc., the relation among σm, KIC and Smf was investigated for Mn-Zn ferrite (KIC; 1.3MPa.m1/2, the mean value of σm; 0.18GPa) as an example. In addition, the applicability of equation of σo=σd{1+2(a/ρ)1/2} or σ0-1=σ0-1+2σ0-1ρ-1/2 a1/2, i.e., the applicability of the estimation method of attainable strength (σa; σd or σm at 2a=mean grain size) to Mn-Zn ferrite was also investigated {σo; ideal bending fracture strength, i.e., the strength which is assumed to be obtained when the length (2a) of longer axis of fracture source becomes imaginarily zero, although the actual attainable minimum value of 2a is the mean grain size of the materials, σd; external stress which operated on the fracture source at the moment of fracture, ρ; effective curvature-radius of the edge of fracture source}.
The results obtained were as follows: (1) The linear correlation was found between σm and Smf1/2, in a similar way to the cemented carbide, etc., which indicates that the equation of σm=ΨKICSmf1/2is also applicable to the ferrite or brittle materials with considerably low KIC and σm. The ratio of the slopes of two regression lines of the ferrite and the cemented carbide coincided well with the ratio of the measured KIC values of both materials. This indicates that the Vvalue in equation ofσm=ΨKICSmf1/2 of this ferrite was nearly equal to that of the cemented carbide; the ψ values of both materials were about 15×103m-3/2. (2)The equation of σd-1=σ0-1+2σ0-1+2σ0-1ρ-1/2a1/2 also held for the ferrite. The σa of this material was estimated to be about 0.26GPa, which was about 44% higher than the measured mean value of σm (0.18GPa).View full abstractDownload PDF (4073K) -
Naoki Matsuoka, Yoshihiko Doi, Koji Hayashi1998 Volume 45 Issue 6 Pages 535-543
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn the previous work, we have derived a differential equation for the numerical calculation of the abnormal growth of WC grains in WC-VC-Co fine grained hardmetal, based on grain-dispersed alloy model with two kinds of grain sizes (2-grain-size model) where the rate-determining step of Ostwald ripening of WC grains is the interface reaction, and then numerically estimated the initial sizes of small and large grains where the abnormal grain growth occurs. In this work, first we derived differential equations for calculating each grain size and mean grain size in alloy model with three kinds of grain sizes (3-grain-size model), secondly calculated the large grain size and mean grain size after sintering for WC-0.5mass%VC-l0mass%Co fine grained hardmetal as a function of initial sizes of three kinds of grains and their initial mass fractions, and finally estimated both more detailed conditions for the occurrence or non-occurrence of the abnormal grain growth and the mean grain size.View full abstractDownload PDF (866K) -
Naoki Matsuoka, Yoshihiko Doi, Koji Hayashi1998 Volume 45 Issue 6 Pages 544-552
Published: June 15, 1998
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSIn order to evaluate quantitatively the initial mean grain size (do) and the grain size distribution (σo) for the occurrences of the considerable grain growth and abnormal grain microstructure observed in fine grained hardmetals, the grain growth was simulated by numerical calculation based on multi-grain size model where the rate-determining step of Ostwald ripening is the interface reaction (precipitation), following the previous studies based on 2- and 3- grain size models.
The results obtained were as follows: (1) The following three equations were derived for the growth of grains except for the smallest grain, the extinction of the smallest grain, and the mean grain size, respectively.
di, t+Δt=di, t+(81/32)K(1/dmin, t-1/di, t)Δtdmin, t+Δt-(81/32)⋅K⋅(1/dmin, t2Fmin, t)[NOΣi=min+{di, t2Fi, t(1/dmin, t-1/di, t)}]⋅Δt-dt=NOΣi=min(Fi, t⋅di, t)
where K is (32/81)4(2CoσKVm2/vRT) and is the same as K in well-known equation of d12-d02=Kt. The value of K measured for typical fine grained WC-0.5mass%VC-10mass%Co hardmetal is 2.18×10-2μm2/ks in the case of sintering at 1673K for 0-10.8ks.
(2) In the case of monomodal (normal) distribution of WC grain size, the abnormal grain microstructure dose not occur even at d0 less than 0.2-0.lμm for the sintering at 1673K for 3.6ks. However, the considerable grain growth occurs and the mean grain size (d3.6) of the sintered alloy becomes above about 0.4μm, irrespective of the value of σo. The result is similar to that obtained by 3-grain size model. (3) In the case of bimodal distribution consisting two kinds of normal distributions, the abnormal grain microstructure occurs when the total number of grains in the second distribution is extremely smaller than that in the first distribution and also the initial ratio of the mean grain size (d02m) in the second distribution to that in the first distribution (d01m) is above about 9, for example in the case of d01m(≅d0)=0.1μm. The d3.6 is nearly the same as that in the monomodal distribution. The result is similar to that obtained by 2-grain size model. (4) From these results, it was suggested that the fine grained hardmetal with mean grain size less than 0.3μm is substantially difficult to be fabricated by controlling the initial distribution of WC powder as well as the initial mean grain size, as far as VC (5mass% to Co) is used as the grain growth inhibitor.View full abstractDownload PDF (873K) -
Room Temperature Microplasticity and High Temperature Internal Friction of Mo2FeB2 Based Hard AlloysTeruaki Yagi, Ken-ichi Takagi, Nobuyuki Momozawa, Katsuhiro Nishiyama1998 Volume 45 Issue 6 Pages 553-560
Published: June 15, 1998
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSInfluence of strain amplitude and temperature on the internal friction of Mo2FeB2 based hard alloys were measured by torsional vibration method. The strain amplitude dependency of internal friction was observed. It became clear from the study about Granato-Lücke plots that the mechanism of this relaxation is attributed to break away model of dislocation. It was observed that microplasticity at room temperature appeared in order of C70(Mo2FeB2-54%iron based binder(10%Cr, 5%Ni)), V31(Mo2FeB2-34%iron based binder(6%Cr, 6%Ni)), H71(Mo2FeB2-54%iron based binder(17%Cr, 19%Ni)). In the temperature dependency of internal friction of the hard alloys containing martensite phase in the bonding phase, relaxation peak caused by the phase transformation from austenite phase to martensite phase was appeared at 1033-1068 K and its activation energy and phase transformation temperature were 140-145 kJ/mol and 1093-1173 K, respectively. At following high temperature, a conspicuous increase of the internal friction probably based on plastic flow of the grain boundary was observed. Its activation energy was 106-218 kJ/mol.View full abstractDownload PDF (2867K) -
Toshio Ishii, Nobuhiko Shima, Hiroshi Ueda, Masayuki Gonda1998 Volume 45 Issue 6 Pages 561-565
Published: June 15, 1998
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSCemented carbide cutting tools coated with a TiN layer, a MT-Ti(C, N) layer, a bonding layer and a α-A12O3 layer in subsequent process steps in a hot wall Chemical Vapor Deposition (CVD) reactor have been developed, whose lifetime was about twice as long as that of the ordinary K-A12O3 coated ones in cutting tests on a cast metal FC250 due to the improved adherence of α-A12O3 layer.
The CVD coatings of the developed cutting tools have been investigated using X-ray diffraction, SEM, EPMA, TEM and TEM-EDX, and the following characterisTiCs were found:
(1) The bonding layer grains consisted of Ti, C, N and O, or of Ti, C and O.
(2) The crystal structure of the bonding layer phase were found to be face centered cubic with the latTiCe parameter of 0.431 nm.
(3) The bonding layer grains grew epitaxially on the MT-Ti(C, N) layer grains.
(4) No disorder of latTiCe fringes in some interfaces between the bonding layer grains and the α-Al2O3 layer grains could be found.
The facts (3) and (4) among these were considered to be the causes for the improved lifetime or adherence of the α-Al2O3 layer.View full abstractDownload PDF (4343K) -
Kazuhiko Tsuchiya, Osamu Terada, Tadao Matsuhashi, Hisashi Suzuki1998 Volume 45 Issue 6 Pages 569-573
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIt is well known that shot-peening on cemented carbide tools such as cutting tools coated with hard materials and sliding parts has often been applied. However, the change of surface structure by shot-peening seems scarcely to be so far made clear. Then, the study on this subject for un-coated WC-15mass%Co and -15mass%Ni alloys was undertaken using mullite beads of 80-200 mesh.
It was found that the rate of fracture of surface layer by shot-peening was larger in coarse grained Co and Ni alloys than fine grained alloys, and it was larger in both alloys by use of coarser beads. It was also found that, to get a flat and uniformly fractured surface, the role of microstructures of the alloy and bead size were particularly of importance.View full abstractDownload PDF (6965K) -
Takashi Itoh, Yoshimoto Wanibe1998 Volume 45 Issue 6 Pages 574-580
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn order to investigate the correlation between number and mass bases of both the particle size and shape, the particle size-shape dispersion diagrams were used. On the assumption that the dispersion condition between particle size and shape is expressed with the two dimensional normal distribution laws, the theoretical consideration of the conversion between number and mass bases revealed the equations expressing the correlation between the two bases. The equations of basis conversion derived in this study contain Hatch's equations for the particle size distribution. The average value of the shape distribution changed with the standard deviations of both size and shape distributions and the correlation coefficient between them.View full abstractDownload PDF (468K) -
Jianhui Li, Takashi Goto, Toshio Hirai1998 Volume 45 Issue 6 Pages 581-585
Published: June 15, 1998
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSSi-B system composites were prepared by arc melting using Si and B powders and then annealed in an argon atmosphere. Arc-melted specimens consisted of mainly SiB14 and free Si. SiB6 phase formed at the boundary between SiB14 and free Si at content of 80 to 86mo1%B by the annealing at 1670K. The lattice parameter of SiB14 increased with increasing annealing time due to the change of Si to B content ratio in SiB14 phase. The electrical and thermal conductivity of the composites decreased with increasing annealing time, but the Seebeck coefficient (α) showed maxima at the annealing time around 5.4ks. The greatest dimensionless figure-of-merit (ZT) value obtained in this study was 0.14 at T=1100K.View full abstractDownload PDF (1920K) -
Yoshihiko Takano, Yoshinori Matsumura, Masaru Yoshinaka, Ken Hirota, O ...1998 Volume 45 Issue 6 Pages 586-589
Published: June 15, 1998
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSPyrochlore La2Zr2O7 containing 8 mol% Y2O3 crystallizes at 825°to 885°C from an amorphous material prepared by the hydrazine method. The lattice parameter is α=1.0751 nm; this value is smaller than that (α=1.0793 nm) of pure La2Zr2O7. Dense Y2O3-doped La2Zr2O7 ceramics (99.7% of theoretical) with an average grain size of 3.8 μm have been fabricated by hot isostatic pressing for 2 h at 1500°C and 196 MPa. They exhibit electrical conductivity of 1.6 S⋅m-1 at 1000°C. Activation energies are 0.82 and 0.58 eV for initial (400°-540°C) and final (540°-1000°C) stages, respectively.View full abstractDownload PDF (2052K) -
Hidenobu Ohta, Makoto Takagi, Toru Imura, Yoshihito Kawamura, Akihisa ...1998 Volume 45 Issue 6 Pages 590-595
Published: June 15, 1998
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHigh- strength P/M aluminum alloys of Al-Ni-Y-Co, AI-Si-Ni-Ce and Al-Ti-Fe-TM (TM: Cr, Mo, V, Zr) systems were prepared by extrusion of rapidly solidified powders which were produced by high-pressure He gas atomization. It was found that wear resistance of the P/M aluminum alloys thus prepared was better than that of the conventional aluminum alloys. A189(Ni0.33Y0.54Co0.13)11 alloy had the best wear resistance among the P/M aluminum alloys studied in this experiment. In order to investigate the cause of the difference of wear properties in those P/M aluminum alloys, wear traces and wear particles were analized by EPMA, SEM, TEM and Micro-Vickers hardness measurement. It was found that the hard oxide layer was formed on the surface of the wear trace in Al89(Ni0.33Y0.54Co0.13)11 alloy. However, in the case of Al78.5Si1.9Ni2Ce0.5 alloy, wear particles were included in the surface of the wear trace. It is considered that the oxidation of wear surface and the stability of the formed oxide layer significantly influenced wear resistance of the P/M aluminum alloy.View full abstractDownload PDF (5006K)
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