Effect of W Addition on Microstructure, Mechanical Properties, and Oxidation Behavior of ZrB2-SiC Composites

The ZrB2-SiC composites with refractory metal W of different contents (1vol%, 3vol%, and 5vol%) were prepared by spark plasma sintering. The densification behavior of composites during sintering process was investigated. The influence of W additions on the microstructure evolution, phase composition, mechanical properties, and oxidation behavior of W-doped composites was studied. Results show that the W addition leads to the formation of core-shell structures in the composites, where the ZrB2 grains are considered as the core and the in-situ formed (Zr, W)B-2 solid solution is considered as the shell, thereby effectively promoting the grain refinement and composite densification. Compared with those of the W-free composites, the Vickers hardness, flexural strength, and fracture toughness of W-doped composites are enhanced. The optimal mechanical properties can be achieved at W addition content of 3vol%: the highest hardness, strength, and toughness can be obtained for the composites. The mass gain and oxide scale thickness of composites are gradually decreased with increasing the W addition from 0vol% to 5vol%. When the W addition in composite is 5vol%, the SiC-depleted layer disappears. Finally, the influence mechanism of W addition on the performance of composites is discussed.