Effect of C doping on structure and properties of TiAlCrN coatings by filter cathode vacuum arc deposition

Ultra-hard and wear-resistant (TiAlCrN)C coatings were deposited by filtered cathodic vacuum arc deposition method under the conditions of a fixed N2 flow rate (30 sccm) and an C2H2 flow rate of 0, 5, 10, 30 and 50 sccm. The effect of C2H2 gas flow on the phase structure, mechanical properties, friction properties, as well as corrosion resistance properties of the coating was studied systematically. The results show that C atoms exist in the form of replacing N atoms in the coating, making the coating structure more refined and transforming from a single face-centered cubic (fcc) to an amorphous state. A proper amount of carbon content aggravates the solid solution strengthening and lattice distortion effect of the coating, and increase the hardness of the coating. The coating (Fc = 10 sccm) presents ultra-high hardness (45.95 GPa), excellent wear resistance (1.1 × 10−6 mm3 N−1 m−1) and corrosion resistance properties (2.488 × 10−7 A·cm−2). When excessive carbon was incorporated into the coating (Fc ≥ 10 sccm), a large amount of N was supplanted by C, and the soft amorphous carbon increased in the coating, which reduced the hardness and H/E of the coating, resulting in an increase in the wear rate. The (TiAlCrN)C coating exhibits excellent wear resistance and corrosion resistance, and shows potential application value in surface protection in extreme environments.