Journal of the Japan Society of Powder and Powder Metallurgy

It is the aim of our present investigation to acquire a wider knowledge of the mechanical properties and the dimensional changes and to obtain a deeper insight into the sintering mechanism of the IRON-CARBON-COPPER COMPACTS.
The sintered material of the iron and copper powders is widely used in the new field of powder metallurgy, especially in manufacturing machine parts. It is recognized that the carbon content in steel increases. such mechanical properties as tensile strength and hardness. In order to increase the stegnth of the sintered parts, we use the mixture of reduced sponge iron powder M11100, very fine flaky graphite (-1000 mesh) and fine dendritic electrolytic copper powder.
Some abnormal phenomena have been observed which could not be expected from the results of the study on the iron-carbon and iron-copper systems ; that is the remarkable shrinkage at the points of 6-10% copper and 1-2% graphite contents in case of the iron-carbon-copper compacts, while the iron-copper system shows noticeable COPPER-GROWTH at the copper range 7-9% and the carbon-iron system has the small dimensional changes.

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Some preliminary experiments were made to prepare an electric heat element chiefly composed of MoSi₂ fine powder mixed with oxide powders (Al₂O₃, SiO₂), and the mixture was sintered with hot pressing process. The Optimum sintering conditions were thus made clear. The specimens obtained were subjected to some physical and mechanical tests.
Results were summerized as follows:
(1) The sintering temperature of MoSi₂ with some admixture of oxides (Al₂O₃, SiO₂) was 1600-1650°C and the sintering pressure was 250kg/cm², the density of the specimen attaining 90-97% of the theoretical density.
(2) The corrosion resistance increased with the increasing amount of the oxides added.
(3) Vicher's hardness value of MoSi₂ with oxide admixture was higher than that of pure MoSi₂. They were in the range of 971-1300.
In general, Vicher's hardness in hot temperature decreased as the atmaspheric tempe-rature increased.
(4) The addition of oxides to MoSi₂ made the electrical resistance of the corresponding specimen higher.
(5) The electrical resistance increased linearly with the rise of temperature, for example
0.1×10-2Ω-cm at 1500°C.
(6) The modulus of rapture decreased with the increasing amount the oxides.
(7) The thermal shock resistance increased with the additiou of Al₂O₃.
(8) The oxidizing tests in the air at 1200°C proved successful, The increase in weight of the specimen was in the range of 0.0002-0.0005g/cm²/day.

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