The influence mechanism of slip ring material characteristics on arc erosion resistance

During the long-term operation of hydro-generator excitation systems, the carbon brush–slip ring interface is prone to repeated arc erosion, which seriously affects current-carrying reliability. To reveal the dominant mechanisms responsible for the differences in arc erosion resistance among hydro-generator slip ring materials, arc discharge experiments, three-dimensional profile characterization, SEM/EDS analysis, and material property comparison were performed. The arc erosion resistance was evaluated using comprehensive indicators, including crater morphology, apparent maximum depth, surface integrity, molten-pool stability, and crack features. The results show that the comprehensive arc erosion resistance decreased in the following order: CuW70 > 45G > 16Mn/Q355 > Q235/20G > 7075Al. CuW70 exhibited the best resistance because the preferential melting and evaporation of the Cu phase and the structural constraint of the high-melting-point W skeleton limited molten-pool expansion and crack formation. In contrast, 7075Al showed the most severe damage because its low-melting-point Al matrix promoted rapid softening, molten-pool expansion, material ejection, and graphite adhesion. Among the steels, the erosion behavior was mainly governed by hardness and microstructural stability. The compact pearlite–ferrite structure of 45G improved crack resistance, whereas the ferrite-dominated Q235 and 20G were more susceptible to thermal softening and crack propagation. The damage process can be interpreted as a stage-dependent evolution involving contraction heating, incandescence-critical melting, and arc-discharge-induced material removal. These findings provide a multi-parameter evaluation strategy for selecting arc-erosion-resistant slip ring materials in hydropower applications.