Effect of CH ₄ flow rate on the microstructure and tribological behavior of Ti/W-C/W-DLC gradient coatings on YG12 cemented carbide

To protect WC-Co tools during machining, Ti/W-C/W-DLC compositionally graded coatings were deposited on YG12 cemented carbide via reactive magnetron sputtering. The effect of CH ₄ flow rate (20–40 sccm) was systematically investigated. Results show a 30 sccm flow yields an optimized, dense sp ³ -rich amorphous structure with the lowest I _D /I _G ratio (0.82), suppressing W-catalyzed graphitization. This coating exhibits superior resistance to mechanical deformation and the highest interfacial adhesion (L _c1  = 22 N). Furthermore, tribological tests demonstrate a low friction coefficient (∼0.09) and minimum wear rate (1.7 × 10 ^–7 mm ³ ·N ⁻¹ ·m ⁻¹ ). These findings elucidate hydrocarbon kinetics, providing a structural design strategy for highly wear-resistant cutting tools.