抄録
Simultaneous addition of WC and HfC to TiC-TiN-Mo2C-Cr3C2 composite ceramics was attempted to broaden application field of composite ceramics based on TiC-Cr3C2 system for cutting tool materials. Compacts of the multicomponent ceramics consisting of 40%TiC-15%TiN-4%Mo2C-25%WC-8%HfC-8%Cr3C2 in weight percentage, contained about 1% of metallic impurities of iron group outside the proper components, were sintered at temperatures up to 1600°Cfor 2 hr in a vacuum of 10-4mmHg.
The compacts showed distinguished sinterability similar to TiC-TiN-Mo2C-Cr3C2 composite ceramics: those were attained complete densification by means of sintering at temperature somewhat above 1350°C.
It was confirmed that the same mechanism in densification was taken place in both composite ceramics. Namely, Mo2C was dissolved in TiC in the form of cubic ζ-MoC as a solute readily and preferentially at the temperature up to about 1100°C, resulting formation of (Ti⋅Mo)C solid solution. Preferential formation of the solid solution was promoted dissolution of other components, viz. WC, TiN and Cr3C2, into itself during sintering, which played an important role as the main driving force of densification, especially dissolving of TiN in the final stage of densification.
Metallic impurities in the multicomponent composite ceramics were fully dissolved at temperature up to 1400°C into low-chromium carbides, which have been formed in sintering process as well as in TiC-Cr3C2 system.
The dissolution mechanism of hexagonal WC into TiC in the form of cubic β9-WC phase as a solute was also discussed.
