tungsten metal ''(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 ''(Figs. 2.134 and 2.135) (Table 2.37)''.

During repeated switching under arcing loads tungsten oxides and mixed oxides (silver tungstates – Ag₂ WO₄ ) are formed on the Ag/W surface creating 2 4 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.