The Effect of High Temperature Exposure in Reducing or Oxidizing Atmosphere on Ceramic Joints Brazed with Silver-Copper Oxide

摘要

Silver-copper oxide based reactive air brazing (RAB) technique was developed as an alternative technique for joining complicated ceramic parts. It was found that the addition of copper oxide to silver greatly influences both the wettability and the joint strength of brazed joints. The bend strength of brazed alumina joints increased with CuO content as the wettability of the braze on the alumina substrate improved with CuO addition. To examine the feasibility of this braze for various high temperature applications, brazed alumina joints were exposed to oxidizing and reducing atmospheres at high temperature. The brazed joints, which were exposed in air for 100 h, maintained good bend strength similar to the as-brazed samples. This result indicates the excellent high temperature oxidation resistance of the Ag-CuO based braze. However, exposure of the alumina joints in reducing atmosphere resulted in significant reduction in bend strength. Effects of high temperature exposure on mechanical properties and microstructure of the brazed ceramic joints will be discussed in details.