Argon plasma treatment on metal substrates and effects on diamond-like carbon (DLC) coating properties

The diamond like carbon coatings (DLC) of 400 nm thickness was deposited by filtered cathodic vacuum arc system. The argon plasma etched and non-etched tungsten carbide-cobalt (WC-Co) and stainless steel (SUS) were used as substrates. The chromium was deposited as an interlayer for diamond like carbon coatings on the etched and non-etched WC-Co and SUS substrates. The present research is to evaluate the effect of argon plasma etching of the substrates on microstructure, tribology and adhesion strength of DLC coatings. The films were characterized by field emission scanning electron microscopy, Raman spectroscopy, tribology and scratch tests. The Raman studies showed the broad peak ∼1550 cm⁻¹ indicates the formation of amorphous carbon or diamond-like carbon. It was found that the DLC coatings on the plasma etched substrates of WC-Co and SUS have shown the low friction coefficient of ∼0.12–0.14. The DLC coatings on plasma etched substrates of WC-Co have better adhesion strength. The results showed that the argon plasma etching of substrate reduces the surface roughness to ∼2.5 nm, resulting in smooth morphology, good adhesion and wear resistance as compared to DLC coating on non-etched substrates. The scanning electron microscopic studies showed that the DLC coated specimens with plasma etched substrates have minimum damage as compared to the DLC coated non etched substrates.