| In this thesis, the properties and preparing methods of intermetallic compound NiAl and the development of Ti(C,N)-based cermets were reviewed. Based on the above work, nine Ti(C,N)-based cermets were prepared by replacing a part or the whole of Ni in TiC-10TiN-30Ni-15Mo-7.5WC-1.5C-0.6Cr3C2 (wt%) with NiAl. The influences of NiAl content on the microstructures and properties of Ti(C,N)-based cermets were investigated, in order to supply some theoretic references for their composition design used at higher temperature, by means of centrifugal particle-size analyzer, thermogravitic analyzer (TGA), optical microscopy (OM), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS).According to the microstructure evolutions of two cermets with 20wt% and without NiAl during vacuum sintering, it was found that the initial alloying temperature of the former was 1450℃, which was higher about 200℃than that of the latter. For the former, it didn't obviously alloy at the temperature between 900℃and 1350℃, and it obviously alloyed at the temperature between 1450℃and 1600℃, and it had a classical core-rim microstructure which consisted of ceramic phase Ti(C,N), rim phase (Ti,W,Mo)(C,N), and binder phase NiAl containing much Mo, W and Ti.In the range of 10~30wt% NiAl, ceramic phase became smaller, distributed more evenly, were surrounded completer by rim phase and microstructure became denser with the increase of NiAl content. Moreover, Ti(C,N)-based cermets with 30wt% NiAl had the highest mechanical properties at room temperature which were transverse rupture strength 710MPa and hardness 88.2HRA, and had the lowest liveweight growth after isothermal oxidizing at the temperature between 800℃and 1150℃for 3h which was helpful for their usage at higher temperature. |
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