Influence of brazing process parameters on lifetime-determining characteristics

Vacuum brazing is an effective joining process with high seam quality, especially for components with many joints like the common rail system. Varying the process parameters lead to different seam characteristics and properties. This means, by keeping the material paring of base and filler metal constant, an adjustment of the seam properties for certain application cases can easily be done.
The presented investigations focus on the macro- and microstructural changes of brazed seams produced by vacuum brazing. Shear- and peel specimens, made from stainless steel X5CrNi18-10 and Cu110 brazing filler metal, were manufactured with varying process parameters. The brazing joints were characterized metallographically. The results show a significant influence of the brazing parameters on the surface topology, intermetallic phases and overall seam quality of the brazed specimens. Since the estimation of the fatigue strength for brazing is mostly based on empirical values, the results of this work can be used to develop a calculation-based dimensioning concept for brazed joints, as it already exists for welded connections. The use of an application-oriented dimensioning concept can lead to an overall improvement in brazing quality and a better understanding in the industrial sector.