Improving Tribological Performance of Piston Ring Steel Substrates by DLC/Nano-crystalline Diamond Coating

The goal of this study is to reveal the effects of N 2 incorporation in DLC coatings in terms of carbon bond formation and to understand the tribological behavior of this coating by conducting thorough investigations on the coated substrates. This study reports the effects of diamond-like carbon (DLC) and nano-crystalline diamond (NCD) film on improving tribological behavior under harsh friction conditions. The film was deposited on AISI 1018 low-carbon steel alloy substrates cut from a piston ring of an internal combustion engine via electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) technique at bias voltage of − 600 V using methane (CH 4 ) as carbon source and nitrogen (N 2 ) to crystallize the carbon bonds in DLC/NCD form by varying the flow rates (CH 4 /N 2 plasma). The coated substrates were analyzed in terms of friction and wear (reciprocating friction-wear test module), surface morphology (SEM, AFM), chemical composition (EDX, XRD), hardness, surface roughness, and bond structure (Raman). The film deposited at 8 sccm of N 2 and 6.05 sccm of CH 4 depicted the maximum hardness (47 HRC) and minimum wear rate (6.35*10 –9 mm 3 /Nm) during the abrasion tests. It was evident that DLC/NCD film was deposited on the substrate according to related analyses and the DLC/NCD coating on the piston ring material provides considerable improvements on tribological performance leading to reduced fuel consumption, cleaner and more efficient fired engines.