A study on thick coatings of tetrahedral amorphous carbon deposited by filtered cathode vacuum arc plasma

Thick coatings of tetrahedral amorphous carbon (ta-C) have great existing and potential commercial importance for components such as automobile accessories. We confirmed the feasibility of depositing thick ta-C coating on Si wafer, WC, stainless steel (STS), and Al alloy substrates by a home-made filtered cathode vacuum arc. A ta-C coating of 800 nm thickness was successfully deposited over 20 min continuous coating. Interestingly, coatings with thicknesses exceeding 1 mu m were easily delaminated by thermal and internal stress effects when the coating time exceeded 20 min. Varying the bias (0 V <-> 500 V) was highly effective in controlling the internal stress relaxation of the ta-C. This method showed significant improvements in the stress relaxation of the ta-C coatings. By applying multicycle coating, the thickness and hardness of the ta-C coating could reach 9.3 mu m and 45 GPa, respectively, at a coating speed of 3.0 mu m/h on a fixed substrate.