TiC-Niサーメット内のTiC粒子に関する研究

抄録

The shape and the size of carbide grains in nickel bonded titanium carbides were studied by metallographical methods to confirm the influences of sintering atmosphere, temperature, and of the amount of metal binder on the nature of carbide grains.
The carbide and nickel powders were mixed and ball-milled with methyl alcohol for 25 hours. Thus five titanium-carbide nickel compositions containing 10, 20, 30, 40 and 50 percent Ni by weight were prepared. Besides, another five ones, including 5 percent TiO₂ were also prepared. Compacts of 12mmφ×10mm were pressed with the presure 1t/cm², which were sintered at 1500°C in a graphite boat in either dry hydrogen or argon, and were quenched into water. The specimens were cut in vertical direction into two halves and polished with diamond paste. From the visual observations of microphotographs the statistical measure of grain size as well as the factor describing the grain shape were worked out.
It was found that the size and shape of carbide grains varied with the amount of metal binder, i.e. with the amount of liquid phase existing during the sintering process. function
The specimens containing more than 30 percent Ni showed that the grain sizes was the of the sintering temperature only, being quite inde endent of the composition. Those of less than 20 percent Ni, however, proved that the grain size decreased with decreasing amount of metal binder.
In the absence of oxygen the fraction of angular carbide grains increased with the amount of metal binder, while in the presence of oxygen the increase of spheriform grains was observed. The sintering at lower temperature, 1400°C, showed that the grain growth as well asthe influences of atmosphere and of the amount of metal binder on the grain size were greatly reduced.