Silver Refractory Contact Materials
These contact materials are used extensively in applications where high voltages generate extensive arcing, such as circuit breakers and switchgear. The refractory component (W, WC, Mo) provides durability to the contact, while the silver provides excellent thermal and electrical conductivity. Relative to many other contact materials, silver refractory materials are highly resistive. The use of silver refractory materials typically entails high contact pressures because of the high resistance of the refractory component. When selecting these materials, consideration must be given to the increasing contact resistances that are experienced during service life. The correct selection of compositions, refractory components and particle sizes can often overcome this phenomena.
These dual phase materials are produced exclusively through powder metallurgy techniques, primarily through unit compaction. Compositions can range from 10% to 90% silver. The low ductility of these materials entails unit compaction. Consequently, the materials tend to involve more fabrication than many other contact materials. Refractory contact materials are supplied as discrete contacts with and without brazing alloys flushed to the attachment side. They are also available as furnace, torch and resistance brazed contact assemblies.