Effects of chromium on the interface and bond strength of metal–ceramic joints

In active brazing of alumina and stainless steel using copper-based filler, active elements such as chromium were introduced as additives. The effects of these additives on the microstructure of the interface and bond strength of the joints were investigated. The wetting characteristics of liquid Cu with Cr additives on the alumina substrate have also been studied by a sessile drop method, which indicates that the contact angle can be decreased even to less than 90° due to Cr additive. The segregation of Cr2O3 at the interface between Cu and substrate was observed by SEM and EDS techniques. Through four point bending test, it is found that the additive of Cr in the filler materials can obviously improve the bend strength of the joints. These results demonstrate that the addition of Cr into liquid Cu can improve the wettability of the metal on alumina and facilitate the formation of a strong alumina–metal joint.