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Volume 39, Issue 1
Displaying 1-12 of 12 articles from this issue
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Masahiko Shimada1992 Volume 39 Issue 1 Pages 1-9
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSHigh fracture strength and high fracture toughness of yttria doped tetragonal zirconia polycrystal(Y-TZP), Y-TZP/Al2O3 composites and ceria doped tetragonal zirconia polycrystal(Ce-TZP) were fabricated by post-HIPing technology. The maximum fracture strength of Y-TZP/A12O3 composites was 2400MPa at 30°C. The maximum fracture toughness of Ce-TZP was 20MPam1/2. It was found that hot isostatic pressing was effective to eliminate fracture origins such as pore. Three approaches, alloying Y-TZP with 0-20wt% CeO2, dispersing 0-40wt% A12O2 into Y-TZP and decreasing the grain size of zirconia were examined to control the tetragonal to monoclinic phase transformation by low temperature annealing in air and in water at 60-700°C. The amount of the monoclinic phase formed decreased with increasing CeO2 contents and A12O3 dispersed, and with decreasing the grain size of zirconia. Thermal shock behavior of Y_TZP with various grain sizes was evaluated by the water quenching method and the tetragonal to monoclinic phase transformation was investigated by using Raman microprobe spectroscopy. The critical quenching temperature different of Y-TZP increased from 250°C to 425°C with increasing grain size from 0.4 to 3.0μm.View full abstractDownload PDF (580K) -
Molding Test and Powder FlowabilitySeizo Takahashi, Takeo Nakagawa1992 Volume 39 Issue 1 Pages 10-15
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCompaction of powder to the shape of a deep wall cup, which was difficult to be formed by usual press compacting, was carried out by PPFM (Press Powder Flow Molding). The powder used was pure iron powder with a little resin binder (PVA : Poly Vinyl Alcohol) admixed or with lubricant (ZnSt) and some amount of liquid binder (Liquid Paraffin). Addition of Liquid Paraffin provided an increase in the cup wall density and hence the overall density of the green compact. Especially in case of adding 1.5wt% Liquid Paraffin, the difference in density between the cup wall and the bottom was a small enough to give higher density.
Powder flowability during compaction was estimated from the density distribution in green compact and it could be concluded that the powder flowed from the cup bottom into the wall, because of the lubricating effect of the Liquid Paraffin. One advantage of this method over PIN (Powder Injection Molding) was that good flowability was achieved by the addition of smaller amount of binder.View full abstractDownload PDF (408K) -
Hidenori Kuroki, Masahiro Hiraishi, Takashi Kimura1992 Volume 39 Issue 1 Pages 16-23
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESS18 Cr-8 Ni stainless steel wires 0.160mm and 0.035mm in diameters were wound in layers on core rods of the same steel. Before sintering in hydrogen, the wire layers were cold-pressed in the direction along core axis to form flat contact areas between wires, with widths of one third of the each original wire diameter. Welds between contacting surfaces of wires were observed on sections of the wire layers by optical and scanning-electron microscopes.
The initial stage of sintering begins by the formation of micro welds at some points between contacting surfaces. The welds grow and coalesce with each other eliminating micro pores between them to occupy whole the flat contacts between wires. The activation energy of welding 60% of the flat area is lower than that for grain boundary diffusion of iron in a stainless steel. The energy of welding 90% is similar to that for volume diffusion. Welding rates during the initial stage of sintering are independent on wire diameter. The growth of a whole neck proceeds more rapidly between smaller wires than between larger ones. Curvatures of the necks are independent on wire diameter.View full abstractDownload PDF (3269K) -
Mitsuru Nakamura, Ko-ichi Kamada, Hiroshi Horie, Sadato Hiratsuka1992 Volume 39 Issue 1 Pages 24-27
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSInfluences of the addition of phosphorus and the sintering temperature on the mechanical properties of P/M Austenite type stainless steels were investigated. As a result, the best produced conditions obtaining high mechanical properties on P/M Austenite stainless steels were necessary to add 0.2-0.5wt% phosphorus and to sinter in the range of 1626K to 1673K. The tensile strength, elongation and impact values of these specimens obtained were over 550MPa, 40% and 250J/cm2 respectively. The mechanism of improvement of these mechanical properties was caused by a high sintered density of Austenite matrix obtained by the eutectic reaction between the matrix (δ-phase) and minor phosphide (Fe, Cr)3P.View full abstractDownload PDF (2674K) -
Osamu Kimura, Toshio Kawashima1992 Volume 39 Issue 1 Pages 28-32
Published: January 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSWe have analyzed the thermal expansion mismatch stresses at the vicinity of a cylindrical ceramic-metal compressive joint in which the thermal expansion coefficient of the ceramic member is smaller than that of the metal member. The results of the calculation predict the presence of a large tensile axial stress at the surface of the ceramic member and agree quantitatively with those by the finite element method. Contrarily, in this paper, we treat a tensile cylindrical joint in which the thermal expansion coefficient of the ceramic member is larger than that of the metal member. In this joint, a tensile radial stress or a tensile tangential stress plays a major role in the ceramic member. We discuss their distribution and axial variation in detail.View full abstractDownload PDF (1338K) -
Hajime Iwasaki, Eiji Shorakui1992 Volume 39 Issue 1 Pages 33-38
Published: January 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSDiffusion bonding between iron powder compacts was carried out to investigate an effect of graphite content in powder on bonding strength at several bonding temperatures and bonding pressures. The results are as follows:
(1) Shear strength of both inside and joi t of iron powder compact subjected to diffusion bonding has a maximum value at graphite content of 0.2 wt% at overall bonding temperatures from 973 to 1273 K and bonding pressures from 10 to 60 MPa.
(2) Subsequent sintering at a temperature of 1323 K and for a time of 3.6 ks remarkably improves the shear strength of both inside and joint, which increases linearly with increasing graphite content.
(3) Critical bonding condition to obtain 100% of joint efficiency is a temperature of 1073 to 1173 K and a pressure of 20 to 40 MPa for all graphite contents up to 0.8 wt%.View full abstractDownload PDF (1559K) -
Shunzo Tashima, Masayuki Sumita, Hidenori Kuroki1992 Volume 39 Issue 1 Pages 39-43
Published: January 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA centrifugal compaction process applying a 10-20kG centrifugal force to a slip of ceramic powder in a die has been developed. The slip was prepared by dispersing a submicron(0.22μm) high purity alumina powder in 22-28mass % of ion-exchanged water with a ball mill. The coefficient of viscosity of the slip is 80-2000mP⋅sec.
The compaction process is as follows: 1) when the centrifugal force acts, the alumina particles are sedimented in the bottom part of the die cavity, leaving upper clear water in the top part of the cavity; 2) the centrifugal machine is stopped, and the upper clear water is removed; 3) the bottom of the die is replaced by a porous bottom so as to reduce the moisture in the sediment by about 2 mass % with a 10-20kG centrifugal force applied again to the sediment; 4) after dehydration, the bottom is removed and the compact is stripped from the die.
This process has the following merits;
1) preparing and regulating the slip is easy, because the influence of the slip's concentration and viscosity is small.
2) neither a vacuum unaerating process nor unaerating agents are necessary.
3) compacts with a relative green density level above 60% can be obtained in a short time.
4) there is no contamination from the plaster mold.
5) the time for drying and sintering compacts can be shortened.View full abstractDownload PDF (2221K) -
Takeo Nakagawa, Lihong Zhang, Hiroyuki Noguchi, Nobuyuki Takahashi1992 Volume 39 Issue 1 Pages 44-49
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo solve a problem that an extremely long debinding time is required before sintering in case of the ceramics powder compression molding process, the water binder is used for its easy debinding property in stead of polymer or wax binder. The shape fixing is done by freezing the binding water in the die cavity after compression forming. The vacuum freeze drying is applied for removing the water binder in order to prevent the cracking by the shrinkage of formed powder. It is proved by the experiment that flowability can be improved effectively and samples which have complex shape can be formed easily.View full abstractDownload PDF (5179K) -
Fatigue Characteristics of Ceramics with Multiple CracksMakoto Nishi, Tadaaki Sugita, Kanji Ueda1992 Volume 39 Issue 1 Pages 50-55
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper describes the effects of the number of cracks and crack spacing on fatigue crack growth characteristics of PSZ ceramics, which are required in the strength reliability evaluation of ceramics component. Fatigue fracture toughness testing shows that the life of PSZ ceramics with multiple pre-cracks increases with increasing the number of cracks and the life of PSZ ceramics is changed by the crack spacing. Also as the crack spacing is larger, the growth of crack which does not lead to fracture is more significant. It is confirmed that a linear relationship between the fatigue crack growth rate da/dN and the stress intensity factor range Δ K is exhibited on a logarithmic scale for the PSZ ceramics with multiple cracks as in the case of a single crack. On the other hand, crack growth rate parameters m and -logC, for multiple cracks depend on the number of cracks and the crack spacing. Further, the effect of the number of cracks and crack spacing on statistical characteristics of crack growth rate parameters m and -logC, and fracture toughness value Kfc is discussed by Weibull distribution function.View full abstractDownload PDF (1499K) -
Mitsuo Ueki, Atsushi Fukawa, Hisashi Suzuki1992 Volume 39 Issue 1 Pages 56-60
Published: January 15, 1992
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMechanical properties including cutting performance of nitrogen (N) contained titanium carbide based cermet affected by additional carbides, i.e., tungsten carbide, tantalum carbide or molybdenum carbide, were studied comparing with those of N-free cermet. It was found that the hardness of both cermets generally increased by adding the carbides. It was also found that the wear resistance of N-contaied cermet in turning tests, which was inferior to that of N-free cermet, was never improved. On the other hand, superior resistance to fracture of N-contained cermet in milling tests appeared not to be changed by the carbide addition.View full abstractDownload PDF (1517K) -
Kenzo Fukaura, Hisakichi Sunada, Hisashi Izumi, Katsuya Irie1992 Volume 39 Issue 1 Pages 61-64
Published: January 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSiC whisker reinforced 6061 aluminum composites were fabricated by P/M method. Effect of size of aluminum powder on the tensile and fatigue strength was studied in connection with the microstructure of composites.
The main results obtained are as follows:
(1) By using large powders, SiC whiskers in composite were not distributed uniformly and were oriented irregularly. Moreover, they were shortened during hot extrusion.
(2) The tensile and fatigue strength proportionally increased with SiC whisker volume fraction, however, the strengthening rate per unit whisker volume fraction was fairly large for the composite consolidated by using fine powders.View full abstractDownload PDF (4554K) -
Basic Study on Al2O3/SiCw ToolsToshiyuki Obikawa, Takashi Matsumura, Takahiro Shirakashi1992 Volume 39 Issue 1 Pages 65-71
Published: January 15, 1992
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe anisotropy of silicon carbide whisker reinforced alumina (Al2O3/SiCw) in friction and wear was evaluated by the wear test against Inconel X-750 at high sliding speed. Coefficient of friction of Al2O3/SiCw was greater than that of Al2O3 and varied with direction angle θ by the factor of about two. It gave a maximum at θ=30°, while minimum at θ=150°. Wear rate of Al2O3/SiCw was smaller than that of Al2O3 and varied with θ by the factor of about three. It took maximum values at θ=30° and/or 150°, while minimum values at θ=0° and/or 90°. When θ=150°, however, Al2O3/SiCw hardly differs from Al2O3 in friction and wear. Thus, SiC whisker contributes little to the improvement of wear resistance of Al2O3 at the direction angle.View full abstractDownload PDF (406K)
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