This group of contact materials contains the typically 40-65 wt-% of the very hard and erosion wear resistant tungsten carbide and the high conductivity silver <xr id="fig:fig2.135"/> (Fig. 2.135) <xr id="fig:Physical Properties of-Contact Materials Based"/> (Table 2.36)''. Compared to Ag/W the Ag/WC (SIWODUR C) materials exhibit a higher resistance against contact welding <xr id="tab:tab2.37"/> (Table 2.37). The rise in contact resistance experienced with Ag/W is less pronounced in Ag/WC because during arcing a protective gas layer of CO is formed which limits the reaction of oxygen on the contact surface and therefore the formation of metal oxides.