THE EFFECT OF MULTIWALLED CARBON NANOTUBES ON THE TRIBOLOGICAL PROPERTIES OF NIP-DEPOSITED CAST IRON FOR PISTON RING APPLICATIONS

This study investigates the tribological performance of an electroless NiP–CNT nanocomposite coating developed for cast iron substrates, aiming to enhance the durability of the material for automobile piston ring applications. A low concentration of CNTs (0.5[Formula: see text]g/L) was incorporated into the NiP bath, leveraging their superior strength, heat resistance, and self-lubricating nature. The NiP–CNT nanocomposite coating was synthesized via electroless plating, and its tribological response was assessed across varying temperatures and lubrication states. The coating exhibited a uniform nodular morphology, improved microhardness (from 325 HV for CI to [Formula: see text] HV for NiP–CNT), reduced surface roughness, and refined nanocrystalline structure ([Formula: see text][Formula: see text]nm). Tribological tests performed at room temperature, elevated temperature (350 ∘ C), and boundary-lubricated conditions showed a significant reduction in wear rate and wear depth for the NiP–CNT coating compared with uncoated and NiP-coated substrates. Worn surface analysis revealed smoother tracks, fewer abrasive grooves, and the formation of a stable CNT-assisted tribolayer. Overall, the NiP–CNT coating markedly improved load-bearing capability and wear resistance across all operating conditions.