High-ion-energy and low-temperature deposition of diamond-like carbon (DLC) coatings with pulsed kV bias

The high ion energy produced by the substrate bias is essential to the enhancement of the sp³ content in diamond-like carbon (DLC) coatings and adhesion with the substrate. However, excessive ion energy can turn into heat conversely converting sp³ into sp² undermining the mechanical properties. In this work, pulsed kV bias is applied to increase the carbonous ion energy to increase the sp³ content in DLC coatings and improve the adhesion with the substrate simultaneously while avoiding adverse temperature increase. The high ionized carbonous ions flux is formed by an anode-layer ion source with C₂H₂ gas and Cr/CrC_x/CrC interlayers are introduced between the DLC coating and high-speed steel (HSS) substrate to release the internal stress by high-power impulse magnetron sputtering (HiPIMS). The DLC coatings not only have a large sp³ content, high hardness of 18.5 GPa, a low friction coefficient of 0.12, superior anti-corrosion behaviors,and wear rate of 0.87 × 10⁻¹⁵ m³/N m for 4 h, but also exhibits outstanding adhesion (Lc = 76 N) with the HSS substrate in spite of a DLC coating thickness of 13 μm.