*2.3. Phase Identification by X-ray Diffraction and Scanning Electron Microscopy of the Coating*

Wire specimens were cut into segments (length: 1 cm) using a water-cooled diamond saw (Isomet; Buehler, Lake Bluff, IL, USA). The segments were then placed side-by-side on the sample holder to yield ca. 1 × 1 cm2 specimens. Representative surfaces of the control and DLC-coated wire specimens were analyzed using XRD (Rint-2500; Rigaku, Tokyo, Japan) via a parallel-beam method using Cu–Kα radiation (40 kV; tube current: 100 mA) over *2*θ ranging from 10◦–60◦ at a step size of 0.02◦ and a scan speed of 0.25◦ min<sup>−</sup>1. The XRD patterns were obtained at 25 ◦C and analyzed for phase identification

and quantification using PDXL2 software (Rigaku) based on the International Center for Diffraction Data (ICDD) database.

To observe the DLC-coated layers on a cross-sectioned surface, a wire specimen was encapsulated in an epoxy resin (Epofix; Struers, Copenhagen, Denmark) cross-sectioned with a slow-speed, water-cooled diamond saw (Isomet; Buehler) and then ground and polished using a series of silicon carbide abrasive papers and a final slurry of 0.05-μm alumina particles. All specimens were sputter-coated with pure gold for SEM evaluation (JSM-6610LA; JEOL, Tokyo, Japan); the SEM operated at 15 kV.
