The Mechanical Properties of β-SiAlON Ceramics Joined Using Composite β-SiAlON-Glass Adhesives

The mechanical properties of β-SiAlON ceramics joined using β-SiAlON-glass-forming adhesives consisting of mixed Si³N⁴, Y²O³, Al²O³, and SiO² powders are described. Use of adhesives with a β-SiAlON:glass ratio of 60:40 gave an optimum joint strength of 650 MPa in four-point bending mode, i.e., 85% of that of unbonded material, when joining was carried out at 1600°C for 10 min, under an applied uniaxial pressure of 2 MPa. Bonding pressures in excess of 2 MPa caused excessive compressive creep distortion during the joining operation. The strengths of postjoined HIPed material and HIPed, unbonded material, differed by only 4%, i.e., 975 and 1010 MPa, respectively, which indicates that HIPing reduces the size of critical defects in the joint. Fracture toughness of the joint also improved upon HIPing.