Work recently completed in TWI's Core Research Programme highlights best practice for brazing zirconia.
Zirconia, which is used commercially for wire drawing dies, cutting implements, pressure transducers and golf club heads, is generally joined using techniques such as mechanical fastening and adhesives. However for high temperature applications, including fuel cells and oxygen sensors, techniques such as brazing are required.
When zirconia is vacuum brazed, it undergoes significant (and unsightly) discoloration due to the diffusion of oxygen from the zirconia into the braze.
Factors such as brazing temperature, time and braze composition have been evaluated to establish whether the discoloration has a serious effect on material properties such as strength. From this, TWI has identified a processing window which can be used to achieve sound joints between zirconia-zirconia and zirconia-metal.
Further information on the zirconia brazing process may be obtained from Wendy Hanson at TWI. E-mail: firstname.lastname@example.org