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Volume 23, Issue 1
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[in Japanese]1976 Volume 23 Issue 1 Pages 1-6
Published: February 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (1947K) -
Seishi Yajima, Jozaburo Hayashi, Mamoru Omori1976 Volume 23 Issue 1 Pages 7-10
Published: February 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDodecamethylcyclohexasilane was ring-cleavaged and polymerized at 400°C for 48 hours in an autoclave. The polymer was dissolved in benzene and then, the viscous liquid could be obtained. By the treatment of stretching of a glass rod with the surface of the viscous liquid, fibrous material (10-30μ in diameter) could be obtained. The fibrous materials were heat-treated from room temperature up to 1200°C, 1300°C and 1500°C under vacuum, respectively. The obtained fibers were composed of superfine a-SiC particles (30-70 Å) and tensile strength is about 300 Kg/mm2 in the case of 1300°C heat-treated fiber. Tensile strength of 1200°C and 1500°C heat-treated fibers showed approximately same level of that of 1300°C heat-treated fiber. Why such high cohesive power can be appeared is also discussed in this report.View full abstractDownload PDF (2712K) -
Tetsuo Kato, Katsushi Kusaka1976 Volume 23 Issue 1 Pages 11-19
Published: February 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPressing and sintering of SUS. 316L stainless steel powders were studied under various size distribution and amount of surface oxidation.
The results were summarized as follows:
1) Compressibility was higher with mixtures of about 40/60 coarse/-325 mesh powders (permitting some difference in compacting pressure), mainly because of change in shape with particle size.
2) When vacuum-sintered at temperature above 1200°C, -325 mesh size distribution gave maximum sintered density. In other words, the sintering rate was controlled by mixing ratio of fine powders to coarse powders.
3) Oxide layer of stainles steel powder gave poor compressibility, and also-less densification because of delaying effect on mass transport during sintering.
4) Residual oxide layer (inclusion) affected pore-morphology in sintered materials. Therefore, the mecha-nical properties were appreciably deteriorated under higher sintered density with oxygen-content over 0.3 pct.View full abstractDownload PDF (5551K) -
Yuji Muramatsu, Thoru Takeda1976 Volume 23 Issue 1 Pages 20-24
Published: February 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFine W-Cr alloyed powders (up to 30%Cr) were produced by the carbon and subsequent hydrogen reduction of tungsten and Cr2O3 powder mixtures. The powdèrs produced showed excellent compactibility. The green compact formed at the pressure of 4 ton/cm2 was easy to handle. These powders showed also excellent sintering properties. The densities of alloys sintered at 1500°C for 3 hrs in hydrogen attained over 95% of the theoretical densities.
Although as-sintered alloys consisted of tungsten-rich and chromium-rich coarse phases, after the sub-sequent anneal at 1200°C for 5 hrs these phases became fine and homogeneous.
In these dense alloys, an alloy containing 30% chromium showed good resistance to the oxidation in air in the range of temperature, 1000-1200°C.View full abstractDownload PDF (4244K) -
Yuji Muramatsu, Thoru Takeda1976 Volume 23 Issue 1 Pages 25-30
Published: February 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSW-Cr sintered alloys (up to 30%Cr) containing 0.2-1.0% of palladium were produced from W-Cr alloyed powders and subjected to the oxidation at the temperatures, 1200°C and 1300°C in air. The effect of palladium-addition on the oxidation characteristics of these alloys was examined as a function of chromium content, and the protection mechanism to the oxidation was also examined.
The results were summarized as follows:
1) The oxidation characteristics of W-Cr sintered alloys was markedly influenced by the small addition of palladium. The alloy of W-9.87%Cr-0.2%Pd, for example, failed catastrophically in 2 hrs, while the alloys of W-9.87%Cr-0.41.0%Pd resisted over 1000 hrs to the oxidation at 1300°C in air.
2) The more chromium content increased, the more amount of palladium was required for improving the oxidation resistance of these alloys.
3) The improvement of oxidation resistance in W-Cr-Pd alloys owes the a-Pd phase which precipitates pre-ferentially in the vicinity of grain boundaries. This phase shows not only good oxidation resistance, but also contributes to the formation of the protective Cr2O3 surface layers.View full abstractDownload PDF (2451K) -
Koji Hayashi, Masahide Fukuda, Hisashi Suzuki1976 Volume 23 Issue 1 Pages 31-36
Published: February 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe WC-(6-30)%Co high carbon alloys with mean grain size of about 1.7μ were in vacuum sintered, and subsequently four side surfaces of specimens were ground by diamond wheel to prepare the bending test pieces, or further polished to remove the surface layer associated with the residual compressive stress due to grinding. Two sorts of test pieces in each alloy were Vickers-indentated under various loads at the span center, and used for the transverse-rupture test. The difference in strength between two sorts of test piece was examined in each alloy and the residual compressive stress, which may effectively suppress the crack propagation in WC-Co alloys, was estimated.
The results obtained were as follows: 1) A linear relationship between the difference in strength and the depth of Vickers indentation was observed within the accuracy of this experiment, and the value obtained by extrapolating the straight line to zero depth of indentation was considered to he an effective compressive stress (σre) on the surface of ground specimen. The σre of 6, 10 and 30%Co alloys, for example, was about 160, 100 and 10 kg/mm2, respectively; showing that the value decreased sharply with increasing Co content of the alloy. 2) The difference in strength was not almost affected in each alloy by the depth of Vickers indentation. Namely, the strength of ground specimens having indentation was usually higher by about are than that of polished specimens. Under the same depth of indentation, the strength of ground specimens did not almost change with the Cc content, although that of polished specimens decreased by a large amount with decreasing Co contents. Discussions on those results as well as on are were made.View full abstractDownload PDF (417K)
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