Carbon-based coatings (WC/WCN/CNx) were deposited by high power impulse magnetron sputtering and direct current magnetron sputtering on the AISI 52100 alloy; no external heating was applied during deposition. Four bias voltages (−25, −50, −75, and −100 V) were used to analyze the bias effect on coating properties. Hardness was related to the sp3 content, coating adhesion depended on ion flux arriving at the substrate, and amorphous coatings were obtained at higher bias voltage. The coating showed a coefficient of friction of about 0.3, and the wear rate was reduced 100 times. Wear tracks were analyzed by Raman spectroscopy, indicating the graphitization of the coating during sliding.

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