Gradient Structure Evolution During Sintering of WC-TiC-Co Cemented Carbides

Functional gradient sintering of WC-TiC-Co cemented carbides was studied to reveal the effect of powder metallurgical processing conditions on compositional and microstructural, as well as hardness and toughness, gradients. The samples were created by local addition of TiC prior to sintering. Two different starting WC powders, one sub-micron and one medium-coarse, were used. Sintering at two different temperatures of 1410°C and 1475°C was compared. The local addition of TiC created a Ti/Co gradient that affected the structural evolution during sintering. The measured Ti/Co gradient after sintering at 1410°C and 1475°C differed, and the difference was especially apparent for the sample prepared using a sub-micron powder. After sintering at 1475°C, the sample prepared from the sub-micron powder exhibited a large WC grain size gradient and elongated or plate-like WC grains where the Ti concentration was high. In contrast, the sample prepared from the medium-coarse powder only showed a WC grain size gradient and no plate-like WC grain formation. It was also observed that the WC grain surfaces had growth ledges in both samples when the Ti content was enhanced, indicating the influence of Ti on the WC grain growth mechanism.