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→Copper–Tungsten (CUWODUR) Materials
=== Copper–Tungsten (CUWODUR) Materials===
Copper–tungsten (CUWODUR) materials with typically 50-85 wt% tungsten are produced by the infiltration process with the tungsten particle size selected according to the end application [[#figures4|(Figs. 5 – 8)]] (Figs. 2.138 – 2.141) <xr id="figtab:Physical Properties of Copper Tungsten CUWODUR Contact Materials"/> (Table 2.39). To increase the wettability of the tungsten skeleton by copper a small amount of nickel < 1 wt% is added to the starting powder mix.
W/Cu materials exhibit a very high arc erosion resistance <xr id="tab:Contact and Switching Properties of Copper–Tungsten (CUWODUR) Contact Materials"/> (Table 2.40). Compared to silver–tungsten materials they are however less suitable to carry permanent current.
The main application areas for CUWODUR materials are as arcing contacts in load and high power switching in medium and high voltage switchgear as well as electrodes for spark gaps and over voltage arresters <xr id="tab:Application Examples and Forms of Supply for Tungsten– Copper (CUWODUR) Contact Materials"/> (Table 2.41).
<figure figtable id="figtab:Physical Properties of Copper Tungsten CUWODUR Contact Materials">
[[File:Physical Properties of Copper Tungsten CUWODUR Contact Materials.jpg|right|thumb|Physical Properties of Copper Tungsten (CUWODUR) Contact Materials]]
</figurefigtable>
<div id="figures4">
<xr id="fig:Micro structure of W Cu 70 30 G"/> Fig. 2.139: Micro structure of W/Cu 70/30 G