TWI Industrial Member Report Summary 709/2000
K I Ironside and J A Fernie
The last 30 years have seen the development of a range of advanced engineering ceramics such as alumina, silicon carbide, silicon nitride and zirconia. Of these, zirconia (ZrO 2) has joined alumina as a commonly used engineering ceramic in industry. This has happened largely as a result of its low thermal conductivity (0.2 W/m.K), high strength and fracture toughness (particularly at temperatures below ~300°C) and its ionic conduction at elevated temperatures (>600°C).
Mechanical attachment and adhesives are suitable for the joining of zirconia for relatively low temperature applications. For higher temperature applications, brazing is appropriate and in particular active metal brazing. However, during this process, the active element, titanium, reacts with the zirconia, depleting the surface region of oxygen. This has the effect of discolouring (darkening) the zirconia. It is this phenomenon and how it affects the mechanical properties of zirconia that forms the basis of this work.
- To produce brazed zirconia joints and quantify the extent and effect of the known discolouration phenomenon.
- To determine the effect of braze alloy composition and brazing parameters on the strength of zirconia-zirconia and zirconia-metal joints.
- To provide guidance on the brazing conditions to be used for the production of zirconia-zirconia and zirconia-metal joints.