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Volume 33, Issue 8
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[in Japanese]1986 Volume 33 Issue 8 Pages 387-397
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (6280K) -
Shigeaki Takaji, Minoru Nitta, Masaki Kawano1986 Volume 33 Issue 8 Pages 398-401
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe behavior of densification, austenite grain growth and carbide precipitation during sintering of high speed steel powder compacts were investigated. A water-atomized 6W-5Mo-4Cr-2V steel powder was annealed, compacted, sintered, quenched and then submitted to the observation and quantitative measurements of the microstructures.
After the formation of liquid phase along grain boundaries during sintering, the liquid penetrates into solid grain boundaries and disintegrates the solid skeleton into individual crystal grains, causing rapid densification through the rearrangement of the grains. The microstructure during sintering consists mainly of austenite solid grains and a high carbon liquid phase and resembles that of liquid phase sintered heavy alloys. The solid grains grow presumably by a solution-reprecipitation mechanism and the size of the solid grains at the end of the liquid phase sintering corresponds to the final austenite grain size after sintering.
Such microstructures which maintain the configurations during liquid phase sintering can only be observed when the specimens are cooled extremely rapidly after sintering. If the cooling rate is moderate, the liquid phase decomposes into carbide and austenite phases during cooling and the typical microstructure with dispersed carbides is obtained.View full abstractDownload PDF (3146K) -
Nobuyasu Kawai, Minoru Hirano, Tsuneo Tatsuno, Katsuhiko Homma1986 Volume 33 Issue 8 Pages 402-407
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEight kinds of high speed steels in which the primary precipitates such as VC or VN were added to SKH51 matrix composition, were produced by HIP'ing gas atomized powders. The properties of steels after quenched and tempered were studied, and the following results were obtained:
(1) Hardness of VN series steels was slightly lower than that of VC series ones, but its wear rate was almost the same as that of VC series.
(2) Red hardness of VN series was lower than that of VC series.
(3) Bend strength and intermittent cutting performance of VN series were superior to those of VC series.View full abstractDownload PDF (2737K) -
Tadatoshi Honda, Makoto Murai, Katsuhiko Kaneko, Hidenoki Kuroki1986 Volume 33 Issue 8 Pages 408-412
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSStatistical analysis of fatigue strength distribution of sintered smooth specimens prepared from electrolytic iron (Fe) powder, Fe-l mass% graphite (Fe-1 mass%C) and Fe-5 mass%Cu compacts was investigated by the Probit method. The results were summarized as follows:
P-S-N curves for Fe compacts with different density levels, and Fe-1 mass%C and -5 mass%Cu compacts were obtained. Variation coefficients of fatigue strength for Fe compacts and two alloy compacts were within 4.5 to 9.9% and 5.6 to 8.7%, respectively. The scatter in fatigue strength of Fe compacts increased as the sintered density became lower. The inclined parts of S-N curves for Fe-C and -Cu compacts in the stress amplitude range from 196.1 to 274.6 MPa were no significant difference and therefore S-N curves for both the compacts were estimated to be the same.
It was found that the variation coefficients of fatigue strength for smooth specimens of sintered Fe and alloy compacts were smaller than those of cast steel and larger than those of carbon and alloy steels for machine structural use.View full abstractDownload PDF (388K) -
Yoshihiko Doi, Akira Doi, Masaaki Tobioka, Akihiko Ikegaya1986 Volume 33 Issue 8 Pages 413-417
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTiC layer could be deposited on the cemented carbide by plasma assisted CVD process at relatively lower temperatures compared with conventional CVD process. The characteristics of the TiC coated cemented carbide plasma CVD were studied.
It was found that the strength of the TiC coated cemented carbide by plasma CVD was much improved compared with the conventional CVD, and it also showed a satisfactory performance for heavy duty interrupted cutting such as steel milling.View full abstractDownload PDF (2721K) -
Hideo Suzuki, Jun-ichi Ohta, Heihachi Shimada, Ryuzo Watanabe1986 Volume 33 Issue 8 Pages 418-421
Published: November 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSYoung's moduli of some sintered hard materials (WC-CO alloys and hot pressed Si3N4) were measured by Speckle Photography. The advantage of using this strain measurement method was emphasized for the determination of Young's moduli in these hard materials.
The results of this study are summerized as follows:
(1) Young's moduli of the sintered hard materials in this study were found to be uniform along specimen axes under static compression.
(2) It was confirmed that Young's modulus of WC-Co alloys decreases with the increase in Co content, as has been reported before.
(3) In hot pressed Si3N4, Young's modulus along the axis pallarel to the hot pressing direction was found to be larger than that vertical to the hot pressing direction by seven to ten percent.View full abstractDownload PDF (1428K) -
Takeshi Sadahiro, Kaoru Sobata1986 Volume 33 Issue 8 Pages 422-425
Published: November 25, 1986
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffects of loading rate, specimen size and annealing treatment on the fracture toughness of WC-Co alloys were investigated using Bridge Indentation method. This method was compared with Short Bar method and with Microcrack Indentation method for WC-Co alloys and A12O3 base ceramics.
The results obtained are as follows:
(1) Effects of the loading rate and the residual stress at the precrack tips are negligibly small in the case of BI method.
(2) JIS standard specimen for transverse rupture strength is enough to determine the effective fracture toughness of hard materials, using BI method without special apparatus.View full abstractDownload PDF (266K) -
Eiichi Sentoku, Yoshio Fujimura, Hiroshi Kawabata1986 Volume 33 Issue 8 Pages 426-432
Published: November 25, 1986
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe purpose of this paper is to clarify the wear mechanism at high cutting speed where mutual diffusion at interface comes to active.
The relation between the crater wear rate and the condition of diffusion layer by cutting test and dynamic diffusion test, for reference, was investigated and discussed. Combination of materials was cermet tool of TiC type to plain carbon steel of 0.45%C. In the cutting test by turning, cutting speed was varied from 2.5 m/s to 7.5 m/s. In the dynamic diffusion test, the contact planes of both samples inclined at 5 degrees under axial load, were kept at high temperature ranging from 1273 K to 1473 K for 30 minutes in argon gas environment. The surface of samples was observed and analyzed using SEM and EPMA. The main results obtained are as follows:
(1) At a tool face temperature over 1300 K, the wear rate depends strongly upon the temperature.
(2) In this circumstance, a Ti-rich layer on the worn surface of tool is observed, which is hard and a brittle layer of several um thick.
(3) A model can be proposed in which the wear proceeds by the repetition of formation and tearing off of the layer.
(4) The layer is produced as a result of diffusion at interface and squeeze of binding material of Ni by pressure.View full abstractDownload PDF (5222K)
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