Sustainable thick nanodiamond composite coatings on hard metal: Effects of varied discharge energies on tribological performance and corrosion resistance

Sustainable nanodiamond composite (NDC) coatings were deposited on WC − 6%Co substrates using eco-friendly Coaxial Arc Plasma Deposition method at discharge energies of 3.6–9.0 J/pulse. This study optimized discharge energy to enhance adhesion strength, wear resistance, and corrosion resistance, promoting sustainability in preparation and operation of coated cutting tools. NDC coatings, produced without external heating, chemical gases, or cobalt chemical etching, achieved 16 μm thickness with deposition rates ranging from 3.2 to 5.7 μm/h, exhibiting dense and pore-free structures. Hardness peaked at 72.5 GPa at 7.0 J/pulse, slightly decreasing to 65 GPa at 9.0 J/pulse, with Young's modulus showing similar trends. Maximum adhesion strength was 42.5 N achieved at 9.0 J/pulse, attributed to suppressed internal stress at the interface. Wear resistance improved significantly, with wear rates peaking at 1.88E-7 mm 3 /N·m at 7.0 J/pulse, aligning with hardness and C sp 3 content from Raman analysis. The coatings exhibited a low coefficient of friction (0.09), representing a sevenfold reduction compared to uncoated substrates, due to an sp 2 -rich transfer layer enabling enhanced sliding properties. Corrosion resistance improved in 3.5 wt% NaCl solution, achieving 0.5136 mil/year at 7.0 J/pulse, a 60.4 % improvement, though reduced at 9.0 J/pulse due to presence of larger cauliflower-like particles allowing solution penetration. These results highlight NDC coatings as a sustainable and high-performance alternative coating for WC−6%Co cutting tools. • CAPD successfully deposits sustainable NDC coatings with 16 μm thickness. • COF significantly reduced from 0.71 (uncoated WC − 6%Co) to 0.09 after NDC coating. • Wear resistance improved by an order of magnitude with NDC coating (1.88 × 10 −7 mm 3 /N·m). • NDC coating halved corrosion rate of WC − 6%Co hard metal, boosting tool life. • Raman analysis confirms nanostructure of NDC film comprise nanodiamonds and a-C.