Investigation and analysis of arc ablation on WCu electrical contact materials

Abstract

In this paper, arc ablation behavior of tungstencopper (WCu) alloy contacts was investigated by the measurement of weight-loss, or erosion rate, and microstructures of tungsten-copper alloy contacts were examined by using scanning electron microscopy after electrical breakdown process. Experimental results showed that the arc erosion process started at the tiny sharp edges, then the arc spreaded on the second phases, or copper phase on the surface. Because of electrons/ions bombardment, the rapid evaporation and sputtering of liquid copper droplets were serious. As a result, an even contact surface became rugged, and tungsten skeleton remained because of being less eroded. With the increase of applied breakdown voltage, the ablation of tungsten-copper alloy became more significant. The WCu alloys with a higher content of copper showed more severe erosion rate as compared with that with a higher tungsten content under the same erosion conditions. Furthermore, when the number of breakdown is less, WCu alloys with a high copper content are easier for erosion for the conditions of fewer numbers of breakdowns. Whereas, WCu alloys with a high content of tungsten are easier for ablation for the conditions with many times of arc breakdown.

Infiltration sintering of WCu alloys from copper-coated tungsten composite powders for superior mechanical properties and arc-ablation resistance

“…In the initial stage, the mass loss of both the two types of W70Cu30 alloys is quite large because some burrs and other oxide are inevitably existed on the surface of alloy. They are easily subjected to arc breakdown, and local heating or ion sputtering can be generated, thus resulting in the rapid removal of those attachments on the surfaces, which was often called old-refine stage [5]. However, the mass loss increases after this as the removed W and Cu vapors would react with SF 6 (an arc-extinguishing medium) at the high arc temperature, the main recation is shown in…”

“…WCu alloys are widely used as electrical contact materials in high-voltage circuit breakers due to their high melting point, high hardness, low coefficient of thermal expansion (CTE), good arc erosion resistance of W, and remarkable thermal and electrical conductivities of Cu [1][2][3][4][5][6][7][8]. Phenomena of melting/evaporation, or sputtering of contact materials are commonly observed during their services when the high voltage circuit breakers are subjected to breaking current operations.…”

Copper/graphene composites: a review

“…Speciality Cu alloys that could benefit from graphene additions are the copper-tungsten (CuW) or tungstencopper (WCu) materials. As Cu and W are not mutually soluble, these materials are composed of one metal dispersed in a matrix of the other [75][76][77]. Therefore, they are actually MMCs or pseudo-alloys of Cu and W rather than true alloys.…”

Synergistic enhancing effect for mechanical and electrical properties of tungsten copper composites using spark plasma infiltrating sintering of copper-coated graphene

“…WCu contact materials, extensively used as the key components of high-voltage circuit breakers, can efficiently transport electrical currents, however, they experience a high-temperature arc erosion over time. When the power is suddenly switched on/off, significant arcs can be easily generated and accumulated on the contact surface, thus resulting in the early failure of the material 2 . Extensive studies have been undertaken to investigate the electrical properties and arc characteristics of the WCu contact materials.…”