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Volume 17, Issue 8
Displaying 1-10 of 10 articles from this issue
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Takao Kawakita, Mineo Onoda, Nobuhito Kuroishi, Isao Iwaki1971 Volume 17 Issue 8 Pages 331-337
Published: May 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe tensile, impact and fatigue properties, and the fracture mechanism of forged super-high-density sintered steels were investigated in comparison with those of conventional sintered steels and cast wrought steels.
It was found that mechanical properties of the forged sintered steel of the density 7.80 g/cm3 almost reach the level of that of cast wrought materials.
Optical or scanning electron microscopic observation of fracture surfaces of the specimens proved that the fatigue process and the fracture mechanism of forged super-high-density sintered steels were similar to those of cast wrought steels while the fracture in the conventional low density sintered steels occurred along pores in the compacts.View full abstractDownload PDF (4949K) -
Akio Hara1971 Volume 17 Issue 8 Pages 338-341
Published: May 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIt is one of the most important factors to control the carbon content severelyin manufacturing the cemented carbides. Even in the region where neither the phase nor free carbon phase appears, the mechanical properties of the cemented carbides are affected by the change of the Co phase. Therefore a very precise control of carbon content, (less than ±0.05%), is required.
Since the starting powders have a large specific surface, an oxidation on the surface appears to be easily occured. This oxidation causes the decarburization during sintering, and so it is also very important to keep the degree of oxidation below a certain level. In this paper the oxidation mechanism of such powders is studied.
First, the corrosion mechanism in atmosphere of the block metal and some reports on the powder oxidation were reviewed. Investigation on the Co, WC and WC-Co mixed powders, which are usually used for producing commercial cemented carbides, were shown. As a result, the oxidation mechanism on such powders was considered the same as that of the block metal. This is to say, the hydroxide formation (corrosion reaction) is presumed on the surface of the powders.View full abstractDownload PDF (228K) -
Hisashi Suzuki, Kozi Hayashi, Osamu Terada1971 Volume 17 Issue 8 Pages 342-346
Published: May 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe range of two-phase region and the binder or carbide phase composition in the phase region in TiC-Ni alloy were examined in relation to the characteristics of starting titanium carbide powders. The starting powders were prepared from TiO2 and TiH2. Produced titanium carbides have various carbon contents from 17.20 to 19.55%. Five sorts of TiC-30%Ni alloy systems, each different, according to the starting powders used, were vacuum-sintered at 1400°C for 1.5 hr. In each alloy system, the carbon content was strictly controlled and the various alloys with various carbon contents were sintered.
The results obtained were as follows; it was concluded that the range of two-phase region or the compositions of both phases in the alloy systems were not affected by the characteristics of starting powders so far as the alloy systems could successfully be sintered. For example, the two-phase region was found in such cases to exist in the range of about 18.1-19.3% in carbide (converted values of carbon content of alloy to carbide). The maximum carbon content of this 19.3% (actual carbon content in carbide phase, 19.2%) appeared to be controlled by the dissolution of nickel in carbide. It has been suggested that the reasonable combined.carbon of starting titanium carbide powder needed for TiC base cermets should be in the range of at most about 18.5-19.2%, when the oxygen content in starting powders is less than about 0.1%.View full abstractDownload PDF (2409K) -
Yoshio Fujiwara, Hidekazu Doi, Yuzo Oosawa, Kazuo Miyake1971 Volume 17 Issue 8 Pages 347-354
Published: May 25, 1971
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSPlastic deformation and fracture of WC-Co alloys in tension have been studied as a function of composition (6-24wt%Co), WC particle-size (1.3-2.4μ) and carbon concentration.
Although tensile fracture-strain of the alloys is in general much less than compressive fracture-strain, the tensile stress-strain curves can completely be superposed on the compressive stress-strain curves. This result suggests that the deformation mechanisms are same in tension and in compression, i.e., of dispersion strengthening type.
The tensile strengths of the alloys with an optimum carbon concentration and a fixed WC particle-size plotted against the mean free path give rise to a peak at-0.4μ. With the decrease in WC particle-size, the strength curve in general shifts towards higher strength side and the increase in ductility is also accompanied.
Fractographic analysis by means of scanning electron microscopy reveals that tensile fracture is predominantly intergranular. Internal friction of the alloys in general increases with progress of the plastic deformation and also after the fracture even when the fracture occurs essentially in the elastic range. This suggests that plastic straining due to stress relaxation has occurred in the Co phase in some stage of tensile deformation.
Nature of tensile fracture of the alloys was discussed in some detail on the basis of the above observations.View full abstractDownload PDF (2617K) -
On the Wear Anisotropy of AluminaYoshimichi Hara, Mitsuhiko Furukawa, Tadaaki Sugita1971 Volume 17 Issue 8 Pages 355-360
Published: May 25, 1971
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe wear resistance of single crystal of alumina is determined as a function of crystallographic orientation with respect to the rubbing plane and direction. In this case, it is usually found that there are a typical anisotropy of the wear between basal and prismatic planes, and some evidences of plastic flow at the wear surface planes in the wear test. Also, the wear anisotropy in single crystal of alumina depends upon contact load and sliding speed. Since c-axis of alumina crystal is preferably oriented along the pressing direction during hot pressing, in this paper, the effect of this preferred orientation on the wear resistance of hot pressed alumina was compared with the wear anisotropy in the single crystal. From the microstructural observations and some other experimental results, it was shown that the wear mechanism of hot pressed polycrystalline alumina can be understood from that of the single crystal.View full abstractDownload PDF (4251K) -
1971 Volume 17 Issue 8 Pages e1a-e2
Published: 1971
Released on J-STAGE: May 22, 2009
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1971 Volume 17 Issue 8 Pages e1b-e2
Published: 1971
Released on J-STAGE: May 22, 2009
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1971 Volume 17 Issue 8 Pages e1c-e2
Published: 1971
Released on J-STAGE: May 22, 2009
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1971 Volume 17 Issue 8 Pages e1d-e2
Published: 1971
Released on J-STAGE: May 22, 2009
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1971 Volume 17 Issue 8 Pages e1e-e2
Published: 1971
Released on J-STAGE: May 22, 2009
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