INTERFACIAL CHARACTERISTICS FOR ACTIVE BRAZING OF ALUMINA TO SUPERALLOYS

The brazing of alumina to Ni-base superalloy (Inconel 600) and Co-base superalloy (UMCo-50) has been studied. The Ag-Cu-Ti active filler met als with Ti-contents of 2 wt% and 8% wt% were employed in this study. However, experiments showed that the Ag-Cu-2 wt% Ti resulted in poor b onding, which was not suitable for the brazing. With an increase of th e Ti-content to 8 wt%, whey could be bonded. However, the bonding stre ngths were still too low. The four-point bending strengths in this cas e were only 43-54 MPa. An improvement of the bending strength was achi eved by inserting a Kovar interlayer. In this case, the bending streng th was dramatically increased to 240 MPa and 226 MPa for alumina/UMCo- 50 joint and alumina/Inconel 600 joint, respectively.