Silver/Tungsten alloys containing between 25 and 50% silver are used for electrical contacts. These materials are produced via powder metallurgical techniques due to their widely different melting points.
Tungsten oxides and tungstates form on the surface of these metals. This can lead to increasing contact resistance over time.
If more arc resistance is required then these materials can withstand or if contact resistance becomes a problem, silver/tungsten carbide materials offer an alternative.
Silver/Tungsten metals combine the high thermal and electrical conductivities of silver with the arc resistance of tungsten.
As mentioned above, silver/tungsten materials are used for electrical contacts. Typically they are used in heavy duty devices subject to high currents. The presence of the refractory material tungsten, reduces the chances of welding and improves resistance to arc erosion. Optimal compositions are found by balancing conductivity and non-welding properties.
Devices that utilise silver/tungsten materials include:
- Circuit breakers (often in the 50-100Amp range)
- Relays that require good arc resistance