In order to improve the length of plasma into the whole tube and mechanical properties of Cr films deposited on inner surface of tube, a high-power impulse magnetron sputtering (HiPIMS) coating method with planar cathode target and auxiliary anode was proposed. The auxiliary anode was placed near the tube tail to attract plasma into the inner part of the tube. Cr films was deposited on the inner wall of 20# carbon steel tube with diameter of 40 mm and length of 120 mm. The influence of auxiliary-anode voltage on the discharge characteristics of Cr target, and the structure and mechanical properties of Cr films deposited on the inner surface of tube were explored. With higher auxiliary anode voltage, an increase of substrate current was observed, especially in tube tail. The thickness uniformity, compactness, hardness and H/E ratios of the Cr films deposited on the inner surface of tube increased with the increase of auxiliary anode voltage. The Cr films deposited with auxiliary anode voltage of 60 V exhibited the highest hardness of 9.6 GPa and the lowest friction coefficient of 0.68.
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