JOINING OF ZIRCONIA TO ZIRCONIA USING AG-CU-TI FILLER METAL

The active brazing of partially stabilized ZrO2 to ZrO2 was carried out using Ag57Cu38Ti5 filler metal in a vacuum of 7 x 10(-3) Pa. The effects of joining conditions such as temperature (from 1073 to 1323 K) and holding time (from 0 to 60 min) on the joint strength and the interfacial reaction were investigated. The joint strength was evaluated by shear testing. It was shown that the brazing temperature and holding time had a strong influence on the joint strength, which latter was controlled mainly by the interfacial morphologies. A lower or higher temperature and a shorter or a longer holding time were disadvantageous to joint strength due to the thinner reaction layer or cracks present at the interface, the maximum joint strength being acheived at 1123 K for 30 min when the interface reaction layer thickness was about 4.4 mu m X-ray diffraction analyses revealed that the reaction products at the interface between zirconia and filler metal were delta-TiO and gamma-AgTi3, and a layer transition structure with a ZrO2/delta-TiO/delta-TiO + gamma-AgTi3/gamma-AgTi3/Ag-Cu formed at the interface.