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

Abstract

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/CrCx/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.