Sintering of NbC0.95 - CryCz composite materials

A study on the preparation technique of composites in the NbC0.95 - CryCz system is presented. It was found that, in comparison to samples of pure niobium carbide, chromium carbide additives lead to a decrease of the temperature at which shrinkage of the powder compacts starts. At temperatures lower than the temperature of the beginning of shrinkage, solid solutions of Cr and Nb carbides form. Microstructural observations indicate that a liquid phase appears at temperatures higher than the melting point of chromium carbide. It penetrates the niobium carbide matrix grain boundaries. This liquid phase improves densification of the systems and accelerates grain growth. In order to obtain fine-grained materials very high heating rate is necessary. Fully densified composites were received when the rate of temperature increase was equal to 30 °C/min.