Quantitative investigation of material erosion caused by high-pressure discharges in air and nitrogen

Abstract

Quantitative investigation of material erosion caused by high-pressure discharges in air and nitrogenSingle-spark erosion experiments were conducted in different pure metal samples. The samples were used as the cathode, and a platinum electrode was used as the anode. The sparks were produced at high pressure and room temperature, having at this conditions a breakdown phase (ca. 100 ns) and an arc phase (several hundreds of ls). The crater volumes on the different materials were correlated with several properties of materials, in view of different models of material erosion related to melting enthalpy, vaporization enthalpy and sublimation energy. It was found that the quotient between the eroded volume and the spark energy correlates well with a function of the energy necessary to heat the material up to the melting point and to melt it. The particle ejection model can be used to explain this process. Moreover, it was found that the crater shape is related to the surface tension of the molten material. These investigations may be relevant for the development of high-performance materials for electrode and contact applications.

Oxidation Damage of Spark Plug Electrodes

“…Lasagni et al [11] evaluated these three mechanisms and found that the erosion in single-spark experiments correlates well with the melting enthalpy. Hence, the particle ejection model seems to describe this process most suitably.…”

Investigation of the interaction between electrical discharges and low resistivity silicon substrates

“…Reviewing similar experiments under gas atmosphere in metals basically two different kinds of erosion structures can be observed [3,4,15]. One representative is an erosion structure which has the typical form of a crater with a depth in the middle and rims of displaced materials at the sides.…”

“…This indicates that the energy input by ion bombardment and joule heating produces a melting of the material and the plasma forces acting on the molten silicon cause the displacement. According to Lasagni et al [4] the surface tension of the molten material plays an important role when the crater is formed. For relative low values of the surface tension like in aluminium (914 mN/m), tin (544 mN/m) and lead (468 mN/m), the craters exhibit the normal behaviour.…”

“…For comparison, Fig. 5a yields the discharge characteristics for Pt which can be regarded as a typical representative for metals, except for those with a very low melting point, such as lead (Pb) and tin (Sn) [4]. The peak at the beginning may reach about 5 kV which is cut for clarity purposes.…”

“…Therefore, basic research activities focus on discharge related phenomena on metallic probes under vacuum conditions [1,2], but also experiments where the gap between the electrodes is filled with a gas at atmospheric or higher pressure are of high importance [3,4]. The aim to reduce degradation effects caused on electrodes during operation is not only restricted to metals, but also to semi-conducting materials.…”