Effect of Ta content in ta-C:Ta coatings on cutting performance of aluminum alloy

Tetrahedral amorphous carbon (ta-C) coatings are widely applied in machining aluminum alloys to suppress adhesion and wear. However, further improvements in anti-adhesion properties and coating adhesion strength are required under severe cutting conditions. In this study, Ta-doped DLC (ta-C:Ta) coatings with varying Ta contents were prepared and evaluated through cutting tests on ADC12 aluminum alloy, tribological measurements, and adhesion strength tests. Increasing Ta content led to higher friction coefficients and specific wear rates, whereas scratch adhesion tests showed improved critical load associated with reduced residual compressive stress. Among the tested coatings, ta-C:Ta1.1 exhibited the best performance, demonstrating reduced tool wear and lower cutting forces compared with undoped ta-C and higher-Ta coatings. This superior durability is attributed to a favorable balance between high hardness and relaxed compressive stress. The presence of dispersed TaC nanocrystals further suggests enhanced crack resistance, indicating that controlled nanoscale Ta doping is a promising route to achieve both hardness and toughness in ta-C coatings.