Abstract
Oxide-carbide composites have excellent mechanical properties. However, the composites have not been so extensively applied to industrial use because of the difficulty in pressureless sintering of them. In our work, improvement of pressureless sintering of ZrC-Al2O3 composites is shown. Heating of bare green compact in an argon atmosphere gives a relatively low density of sintered bodies. The change of lattice constant of the ZrC phase, and chemical composition of sintered bodies indicate the incorporation of oxygen into ZrC during firing. The oxygen-containing phase is chemically denoted as ZrC(O), in which oxygen atoms are dissolved into the ZrC of the NaCl type crystal structure. The incorporation is related to alumina evaporation during firing, that hinderes densification. We examine preserving of particle size of ZrC powder during mixing and the alumina encapsulation of specimens during firing to prevent evaporation of specimens and proceed the sintering. Addition of MgO leads to further improvement of sintered density, i.e., the relative density of ZrC25-Al2O3 75vol% composite exceeded 98%. We discuss the pressureless sintering behavior of ZrC(O)-Al2O3 composites comparing it with that of TiC(O)-Al2O3 composites as we previously reported.
