The influence of Mo 2 C additions on the microstructural development and sintering response of TiN-Ni 3 Al cermets

Abstract The objectives of this work were to assess the effects of incorporating Mo 2 C additions into TiN-Ni 3 Al cermets, in terms of their densification response and microstructural development. The individual powder components, together with the milled/compacted powder blends were characterised using differential scanning calorimetry and thermogravimetric analysis. Dilatometry was used to determine the densification and sintering response. It is demonstrated that an increase in the Mo 2 C content reduces both the melting and solidification temperature of the Ni 3 Al-based component of the system, which is initially formed via reaction sintering. Crystalline phases were identified using X-ray diffraction, which demonstrated that TiN and Mo 2 C are retained following sintering, and confirmed the formation of Ni 3 Al. The wettability of the Ni 3 Al binder was improved through additions of Mo 2 C, enhancing the densification process. A simple microstructural development model has been outlined, proposing that the Mo 2 C dissolves during liquid phase sintering, and re-precipitates as a shell on TiN grains either during sintering or solidification, which improves the wetting response between the nitride phase and intermetallic binder.