Öz The electromechanical failure of electrodes in the spectral spark sources of the light is prsented. The rise of volumetric electrical spark erosion rate of refractory metals, rustles steels, boron-containing and tungstencontaining alloys and brittle structural constituents at the decreasing of their mechanical properties is established. At the ionic bombardment the electromechanical character of spark erosion of materials can be explained with the thermal shock