Selection and Design of Brazing Fillers for Metal-Ceramic Joints
Three different approaches for metal to ceramic brazing are compared using the example of Si3N4/TiN-steel joints: the use of an active filler metal (single layer brazing system), the metallisation of the ceramic and brazing with a non active filler (two-layer brazing system), the use of a composite brazing filler system (three layer brazing system). Different aspects are analysed: the development of the joint’s microstructure in the as-brazed state, the thermally induced residual stresses and the resulting bend strength of the joint’s strength. With two layers and three layers brazing system, bend strength of about 400 MPa, about 15% higher then single filler metal, were achieved. The three layer brazing system has two advantages: firstly one step processing secondly lower scattering of joint bend strength compared to two layers brazing system. The key factors in all cases are the selection of the brazing fillers and the braze design. In all cases a careful selection of the brazing fillers and the braze design are the key factors. The first criteria for the selection of the brazing fillers for joints of dissimilar materials can be done by considering only the main filler characteristics like titanium content, processing temperature and yield stress. It’s necessary to simulate the joint behaviour by finite element simulation for verifying the final selection of filler metals. It was clearly seen that the plasticity of the filler metal is the main factor affecting residual stresses for the joint geometry in this current work.
T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran
V. Bissig et al., "Selection and Design of Brazing Fillers for Metal-Ceramic Joints", Materials Science Forum, Vols. 539-543, pp. 4008-4012, 2007