Semi-homogeneous joining of silicon nitride with a silicon nitride powder insert

Abstract

Silicon nitride was joined using a silicon nitride powder insert of the same composition as the bulk. The joining was performed at 1600°C for 30 min under a mechanical pressure of 13 MPa. The powder insert was densified to form a joint, but grains in the joint were small and equiaxed. As-joined specimens exhibited an average strength of 859 MPa. During heat treatment at 1800°C for 8 h, grain growth occurred, forming a microstructure with rod-like grains in the joint. The semi-homogeneous joint of the same composition and the similar microstructure consisting of rod-like grains to the bulk was successfully obtained. The average strength of the joined specimen was 947 MPa, which was nearly the same to that of the bulk silicon nitride.