Joining of silicon nitride ceramic composites with Y 2O 3–Al 2O 3–SiO 2 mixtures

Abstract

Hot-pressure sintered silicon nitride ceramic composites were joined to themselves using Y 2O 3–Al 2O 3–SiO 2 mixtures. Reaction behavior at interface between Si 3N 4 and Y 2O 3–Al 2O 3–SiO 2 mixtures during silicon nitride composite joining was studied by means of SEM, EPMA and XRD. The joint strength under different bonding conditions was measured by four-point bending tests. The results of EPMA and XRD analyses show that the liquid glass solders react with silicon nitride at interface, forming the Si 3N 4/Si 2N 2O/Y–Si–Al–O–N glass/Y–Si–Al–O glass gradient interface. From the results of four-point bending tests, it is known that with increasing joining temperature and holding time, the joint strength first increased, reaching a peak, and then decreased. The maximum joining strength of 315 MPa measured by the four-point bending test is achieved for the Si 3N 4 composite–Si 3N 4 composite joint bonded at 1823 K for 15 min. Destructed part is considered to start at the diffusion layer, indicating that the joining strength will be much higher than that value.