Abstract: To toughen Si3N4-based ceramic materials, W/Si3N4 composite ceramic materials were prepared in this article by the pneumatic sintering method with tungsten (W) as the second phase material and Y2O3-Al2O3 as sintering additive. Then the effect of W content on the compactness, mechanical properties, and microstructure of W/Si3N4 composite ceramic materials was investigated. The results indicate that the densities of samples all reach more than 97% when the W content is less than 5% (mass fraction). The most outstanding overall performance of W/Si3N4 composite ceramic materials is obtained when W content is 5% (mass fraction), and the bending strength, hardness, and fracture toughness are (670.28±40.00) MPa, (16.42±0.22) GPa, and (8.04±0.16) MPa·m1/2, respectively, which are 38.08%, 13.08%, and 44.34% higher than Si3N4 ceramic materials without the addition of metal W. By analyzing the microstructure of the polished surface and indentation cracks of W/Si3N4 composite ceramic material samples, it is found that the introduction of W can trigger toughening mechanisms such as deflection and bifurcation of cracks in the propagation path, and consume crack expansion energy, thus improving the fracture toughness of Si3N4 ceramics.
Key words: Si3N4 ceramics, tungsten, pneumatic sintering, microstructure, compactness, bending strength, fracture toughness
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