Strength and microstructure of brazed cemented carbide and silicon nitride joints

Abstract

Successful application of new high-performance cutting materials can only be achieved if adequate joining techniques are provided. Brazing has been proved to be a promising approach for new advanced materials, such as cemented carbides with low binder concentration, or silicon nitride. In this paper mechanical and microstructural results concerning brazed cemented carbide-steel and silicon nitride-steel joints are presented. AgCuTi active braze has been employed as filler metal owing to the fact that both silicon nitride and cemented carbide cannot be wetted by conventional brazes. In order to reduce thermally induced stresses, various interlayer materials have been examined. Microstructural and mechanical analyses revealed that the joint formation as well as interfacial interactions are of great significance for the joint quality. Although the use of interlayers is supposed to be an effective approach to reduce thermally induced stresses in bi-material joints, the influence of microstructural effects within the joint cannot be neglected. The correlation of experimental results with finite element calculations reveals that there are discrepancies. These can be attributed to the fact that FE analyses do not take into account metallurgical effects.