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===Tungsten and Molybdenum (Pure Metals)===
Tungsten is characterized by its advantageous properties of high melting and boiling points, sufficient electrical and thermal conductivity and high hardness and density (<xr id="tab:Mechanical_Properties_of_Tungsten_and_Molybdenum"/><!--(Table 2.35)-->). It is mainly used in the form of brazed contact tips for switching duties , that require a rapid switching sequence , such as horn contacts for cars and trucks.
Molybdenum has a much lesser importance as a contact material since it is less resistant against oxidation than tungsten.
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=== Silver–Tungsten (SIWODUR) Materials===Ag/W (SIWODUR) contact materials combine the high electrical and thermal conductivity of silver with the high arc erosion resistance of the high melting tungsten metal (<xr id="tab:Physical Properties of-Contact Materials Based"/><!--(Table 2.36)-->). The manufacturing of materials with typically 50-80 wt% tungsten is performed by the powder metallurgical processes of liquid phase sintering or by infiltration. Particle size and shape of the starting powders are determining the micro structure and the contact specific properties of this material group (<xr id="fig:Micro structure of Ag W 25 75"/><!--(Fig. 2.134)--> and , <xr id="fig:Micro structure of Ag WC 50 50"/><!--(Fig. 2.135)-->, and <xr id="tab:Contact and Switching Properties of Contact Materials Based on Silver – Tungsten (SIWODUR), Silver–Tungsten Carbide (SIWODUR C) and Silver Molybdenum (SILMODUR)"/><!--(Table 2.37)-->).
During repeated switching under arcing loads , tungsten oxides and mixed oxides (silver tungstates – Ag<sub>2</sub> WO<sub>4</sub> ) are formed on the Ag/W surface , creating poorly conducting layers which increase the contact resistance and by this the temperature rise during current carrying. Because of this fact the Ag/W is paired in many applications with Ag/C contact parts.
Silver–tungsten contact tips are used in a variety of shapes and are produced for the ease of attachment with a fine silver backing layer and quite often an additional thin layer of a brazing alloy. The attachment to contact carriers is usually done by brazing, but also by direct resistance welding for smaller tips.
Ag/W materials are mostly used as the arcing contacts in disconnect switches for higher loads and as the main contacts in small and medium duty power
switches and industrial circuit breakers (<xr id="tab:Contact and Switching Properties of Contact Materials Based on Silver – Tungsten (SIWODUR), Silver–Tungsten Carbide (SIWODUR C) and Silver Molybdenum (SILMODUR)"/><!--(Table 2.38)-->). In north and south america they are also used in large volumes in miniature circuit breakers of small to medium current ratings in domestic wiring as well as for commercial power distribution.
=== Silver–Tungsten Carbide (SIWODUR C) Materials===
