Preparation and characterization of Ti(C,N)-based nano-cermets

Nowadays, preparation of nano-Ti(C,N)-based cermet of high performance remains a big challenge due to the difficulty in dispersion of nano-powder. In the paper, well dispersion of nano-powders was achieved by ultrasonic treatment, surfactant addition and pH value adjustment. The results showed that nano-powder agglomerates can be broken down due to acoustic cavitation effect, but excessive treating time after 40 min was of no avail because of the thermal effect and non-linear effect caused. Tween 80 addition can prevent the agglomeration between nano-particles following stereo-hindrance mechanism. Maximum zeta potential can be achieved by pH value adjustment, which resulted in larger repulsive force and better dispersion according to electrostatic stabilization mechanism. Combined with particle size distribution analysis and TEM observation, 1 vol% Tween 80 addition and pH 4.5 were the favorable parameters for colloidal dispersion, and nano-TiC0.7N0.3–10Mo2C–15Ni cermet with nearly full densification was successfully prepared. The nano-cermet had a finer grain size of about 100–300 nm compared with 0.4–1.0 μm of micro-scaled cermet. The core and rim showed slightly composition difference due to the solid solution reaction of nano-particles and Mo2C occurring before liquid phase sintering. The nano-cermet possessed a higher hardness of 92.8HRA and transverse rupture strength of 1710 MPa than micro-scaled cermet due to the decrease of binder phase mean free path.