Mechanical Properties of β-SiALON⋅β-SiC composites by Pressureless Sintering

β-SiAlON⋅β-SiC composites were prepared from the β-SiAlON powder synthesized by carbo-thermal reduction and β-SiC powder(0-24wt% ) by pressureless sintering. The strength at room temperature of about 800 MPa remained relatively unchanged for composites containing up to 12wt% β-SiC. The strength at 1200°C increased for composites containing up to 9wt% β-SiC. The maximum value was 560 MPa. The fracture toughness for composites containing up to 12wt% β-SiC were higher than that for β-SiAlON alone. The maximum value was 5.4MPa√m for 6wt% β-SiC, and this was improvement of 15% in comparison with β-SiAlON alone. From optical microscope observation, improvement of K1c value was attributed to crack deflections. Vickers hardness increased with increasing β-SiC content, when composites were high density (about 100 %).