Inhomogeneous ablation behaviors and failure mechanism of copper cathode in air

The copper cathode ablation limits the maximum power and operating time of arc heaters significantly.In this work,copper cathodes were tested in an ablation testing system to investigate the ablation behaviors and mechanism of copper cathode in air.The microstructure of the ablated cathodes was analyzed,and the ablation rate was measured.The maximum depth and ablation rate increased with the electronic discharge.The mean ablation rate was compared with the prediction by a thermophysical theoretical model.Many ablation pits formed in the ablated surface and evolved into crater-like structures with unexpected depth as the ablation time was prolonged.The presence of ablation pits and crater-like structures suggested an inhomogeneous ablation behavior of the copper cathode in air.The underlying mechanism is proposed to explain the ablation failure of copper cathode in the high-power arc heater.Future attention to improving the service life of copper cathode could be focused on the surface modification to reduce the ablation inhomogeneity.