Ta-Ni-braze for high temperature stable ceramic - ceramic junctions

Ceramic materials are widely used for high temperature applications. It is still a challenge to produce ceramicceramic or ceramic-metal junctions which are stable at temperatures above 1000 °C using metallic brazes. There are very few solutions for those junctions which are either limited for specific applications or costly. A potential braze for high temperature applications (> 1000 °C) could be a Ta-Ni alloy which we started to develop recently. This paper presents investigations of Ta-Ni alloy with eutectic composition of 38 at% Ta + 62 at% Ni for brazing particularly alumina samples. The melting temperature of the above composition lies at 1395 °C. Specific additives are suitable to promote the wetting of the braze to ceramic materials. Interactions of the metallic braze and the ceramic material influence properties and behavior of the junction as well. Structural features, phase formation during brazing process, mechanical and thermal behavior are investigated in relation to brazing temperature. FESEM, EDX, XRD and thermal analysis methods deliver results about the properties above. Finally a perspective view is given to the potential of Ta-Ni brazes for ceramic-ceramic or ceramic-metal joining with a look to further work which needs to be done.