Effect of MoSi₂ Adding Amount on Properties of α-Sialon Ceramics by Spark Plasma Sintering

Using Y₂O₃ as sintering aid, α-Sialon ceramics with MoSi₂ as a second phase were prepared by spark plasma sintering. The effect of the MoSi₂ adding amount (0-10wt%) on the microstructure and properties of the ceramics was studied. The results show that after adding MoSi₂, the α-Sialon grains in the ceramics changed from equiaxed to long rod-like. With increasing MoSi₂ adding amount, the long rod-like α-Sialon grains increased significantly, and the aspect ratio increased; when the addition of MoSi₂ was 10wt%, the grain size exhibited a significant bimodal distribution. When the addition of MoSi₂ increased from 0 to 10wt%, the relative density of the ceramics increased from 99.0% to 99.7%, the hardness decreased from 21.12 GPa to 20.44 GPa, and the fracture toughness increased from 4.80 MPa·m^1/2 to 6.13 MPa·m^1/2. In dry cutting of nickel-based superalloy, the cutting length of the ceramic tool with 10wt% MoSi₂ was 1.5 times that of the ceramic tool without MoSi₂ when it reached the wear standard, indicating the tool had excellent cutting performance; the main wear forms of the tool were flank wear and groove wear, and the main wear mechanisms were adhesive wear and abrasive wear.