Tribological behavior of DLC/AlCrN coatings on heat-treated grey cast iron under SAE 10W-30 lubrication

High contact stress, load, and speed significantly deteriorates the tribological performance of grey cast iron, leads to shorter component life cycle. Heat treatment coupled with coating may significantly enhance component lifespan and tribological performance due to change in substrate physiochemical properties. Thus, this work focused on the influence of heat treatment at 900°C, followed by rapid water quenching, then deposition of DLC and AlCrN coatings. Further, the surface morphology, microstructure, and worn behavior during micro-scratch and tribotest were analyzed. The DLC coating showed highest reduction in friction coefficient (COF) compared to AlCrN due to its high hardness by 36.3, 21.2, and 16.9% under applied load 40N, 80N, and 120N, respectively. A deep abrasion wear was found on the AlCrN coating, whereas a fine wear mark was observed on the DLC coating under all applied load, owing to least COF and chemically inert behavior of DLC. Although AlCrN exhibits relatively higher wear due to surface defects and its brittle nature compared to DLC but its highest hardness helps in reducing COF from untreated substrate highlighting the role of heat treatment in reducing COF. DLC has superior performance compared to AlCrN for volumetric wear, by reducing wear volume loss of about 9.94%, 5.76%, and 5.29% under static loads of 40N and 80N, and progressive loads of 20–120N, respectively whereas material adhesion was more prominent for AlCrN as confirmed from worn surface morphology.