Influence of filler and base material on the pore development during Reactive Air Brazing

摘要

Innovative and challenging technologies such as solid oxide fuel cells (SOFC) for energy generation make high demands on materials that can often be met by embedding ceramic components into metallic structures. A promising and economic method of joining ceramic to metal or to ceramic is the Reactive Air Brazing (RAB). A disadvantage of the RAB process is the high porosity which can lessen the strength of the joint as well as its corrosion resistance and gas tightness. The pore development in dependence of filler and base materials has been examined during brazing by in situ observations to develop methods to diminish the porosity in the joint. Different stages of pore development can be observed during the brazing process. The pores of the first stage are formed by the vaporising organic binder. In dependence of the filler material and the process parameters these pores are closed by the molten filler. During the melting process small, superficial pores form. On the steel X1CrTiLa22 a third type of pores form above 1000℃. The formation of a gas results in the growth of existing and the appearance of new pores. By adjusting the process parameter this gas and pore formation can be decreased.