HiPIMS–PECVD hybrid strategy enabling HF1-grade adhesion of DLC coatings on Ti–6Al–4V alloy

Achieving robust adhesion of diamond-like carbon (DLC) coatings on Ti–6Al–4V (TC4) remains challenging due to substrate softness and interfacial stress sensitivity. Herein, a HiPIMS–PECVD hybrid strategy was implemented, where HiPIMS was employed for interface activation/densification and PECVD for rapid growth of the DLC functional layer. A Cr interlayer was introduced in both the hybrid coating and the HiPIMS-sputtering reference to ensure identical interfacial conditions for comparison. The hybrid coating (total thickness 1.10 μm) achieved HF1-grade adhesion on TC4 according to VDI 3198, significantly outperforming the HiPIMS–sputtering counterpart. XPS and Raman analyses confirmed a balanced sp²/sp³ carbon network. The coating exhibited a low friction coefficient (0.23), improved wear resistance, and antibacterial rates of 72.9% and 81.5% against Staphylococcus aureus and Escherichia coli , respectively. The results demonstrate that decoupling interface strengthening from functional layer deposition is an effective strategy to overcome the adhesion limitation of DLC on titanium alloys.