Microstructure and mechanical strength of diffusion-bonded silicon nitride-molybdenum joints

Solid-state bonding of reactive systems, such as Si3N4-Mo often results in the formation of excessively thick intermetallic layers that can be detrimental to the final strength of the joint. The objective of this work was to study the microstructural evolution of Si3N4-Mo interfaces, aiming at maximum joint strength via a balance between the fraction of bonded material and the amount of interfacial reaction. Joining was carried out under vacuum or nitrogen atmosphere for temperatures between 1100 and 1800 degrees C. Microstructural analyses of the interfaces revealed the presence of Mo3Si and Mo5Si3 along with residual pores. The results from shear strength tests revealed a strong relationship between the microstructure of the interface and the mechanical strength of the joint. (C) 1999 Elsevier Science Limited. All rights reserved.