A Study of the Carbide Grain in Nickel-Bonded Titanium Carbides
1964 年 5 巻 1 号 p. 8-13
詳細
1964 年 5 巻 1 号 p. 8-13
The effects of sintering atmosphere, temperature and the amount of metal binder on the shape and the size of carbide grains in nickel-bonded titanium carbides were studied by a metallogrsphic method.
Five different mixtures of powders of titanium carbide and nickel, containing 10, 20, 30, 40 and 50 wt% Ni, were prepared by ball milling for 25 hr with methyl alcohol. Besides, the mixtures to which 5% TiO2 was added were also prepared. Compacts of 12 mmφ×10 mm were pressed at 1 t/cm2, which were sintered at 1500°C in a graphite boat in either dry hydrogen or argon and then quenched in water. The specimens were cut into two and polished with diamond paste. The grain size and grain shape were determined statistically from the micrographs.
It was found that the size and shape of carbide grains varied with the amount of metal binder, i.e., the amount of liquid phase existing during the sintering process. The specimens containing more than 30% Ni showed that the grain size was the function of the sintering temperature, being independent of the composition. Those of less than 20% Ni, however, proved that the grain size decreased with the decrease in the amount of metal binder. In the absence of oxysen the fraction of angular carbide grains increased with the amount of metal binder, while in the presence of oxygen the increase of spherical grains was observed. In thecase of the sintering at a temperature as low as 1400°C, the grain growth and the effects of the atmosphere and the amount of metal binder on the grain shape were greatly reduced.
