The influence of adding porous interlayer in the brazing of ceramic to metal

Abstract

In the brazing of ceramic to metal, large coefficient of thermal expansion (CTE) mismatch between both materials will induce high residual stresses, reducing the strength of the joint. In addition, low wettability between ceramic and metal could increase weak phases at the joint interface. A porous interlayer is introduced in the brazing process to overcome the effect of residual stresses and formation of weak phases between ceramic and metal, in this study, the effect of porous interlayer in the brazing of sapphire to Inconel 625 and the brazing of diamond to stainless steel were investigated. Active filler material containing titanium (Ti) was utilized to enhance the wettability of the ceramic-metal joint. It was anticipated that utilizing the porous interlayer for direct brazing would reduce the thermal expansion between both materials. Preliminary experimental results have shown that good bonding between sapphire/filler alloy/porous layer/Inconel 625 was achieved and no voids were detected in the brazing layer. Similar observation was also detected in the brazing of stainless steel/filler alloy/porous interlayer/diamond.