Mechanical property and thermal shock behavior of tungsten-yttria-stabilized zirconia cermet fabricated by spark plasma sintering

The cermet fuels have been considered as a potential key component for the nuclear thermal propulsion, and the homogeneity of the fuel particles in the metal matrix plays a crucial role in stabilizing the structure at extremely high temperatures. In this work, liquid paraffin was used as additive to improve the distribution of yttria-stabilized zirconia (YSZ, an appropriate surrogate for UO2 fuel) microspheres in the tungsten (W) matrix, and the W-YSZ cermet wafers (volume ratio 1:1) with a relative density of 97.6% were fabricated by spark plasma sintering with a specifically designed program. The effects of the paraffin dosage (0–5 wt. %) on the homogeneity, microstructure, mechanical properties, and the thermal conductivity of W-YSZ cermet were investigated. The W-YSZ sample with 2 wt. % paraffin shows the highest homogeneity and exhibits the best comprehensive properties, including the ultimate tensile strength of 132.2 MPa at 600 °C, the bending strength of 455 MPa and thermal conductivity of 50 W·m−1·K−1 at room temperature. Moreover, the cermet could keep structurally sound after thermal shocked at a heat load of 20 MW·m−2. These results would be helpful for the design and optimization of the cermet fuels in the nuclear thermal propulsion.