Cathode erosion hinders the development of high-power arc heaters, and the inhomogeneous erosion of the copper cathode results in catastrophic failures. In this work, the arc erosion behavior of a chromium cathode was investigated compared with copper. The former was relatively homogeneous with shallow erosion pits. The eroded microstructure suggests that the surface chromic oxide layer could suppress the formation of deep craters. The maximum erosion depth and the erosion rate of chromium were lower than those of copper. The single erosion pits on chromium gradually extended and disappeared, suggesting a reduction in the input energy flux density. The underlying mechanism for the homogeneous erosion behavior of the chromium cathode was proposed. The homogeneous erosion behavior of the chromium cathode makes it a promising candidate for high-power arc heaters.
In this study, Ni-Cr alloy coatings were obtained on mild carbon steel surface by direct current (DC) and pulse current (PC) electrodeposition from a kind of acid solution. X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyse the phase structure and surface morphology. The microhardness of the Ni-Cr alloy coatings was evaluated using microhardness tester. The electrochemical behaviour of the Ni-Cr alloy coatings was investigated by polarisation curves and electrochemical impedance spectroscopy (EIS) in 3?5 wt-% NaCl solution. The results indicated that the microstructure and corrosion resistance of the Ni-Cr alloy coatings were greatly affected by electrodeposition method. The PC alloy coatings exhibited more compact surface, higher microhardness and better corrosion resistance compared with those of the DC alloy coatings.
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