Evaluation of Near Frictionless Carbon Coatings Using Four-Ball Wear Tester

Near frictionless carbon (NFC) coatings were deposited in a large-area filtered cathodic arc system by plasma-enhanced chemical vapor deposition. An NFC coating with carbon-enriched TiC bond layers was deposited on half inch diameter steel (M50) balls. The four-ball wear test was used to evaluate the performance of the NFC coating. The endurance limit of the NFC coating was determined by starting the wear test at a relatively low load and increasing the load by a fixed amount after a given time interval to a final load at which the friction force reached a certain level. The four-ball wear test was conducted in fully flooded, starved, and dry lubrication conditions. MIL-PRF-23699 oil was the lubricant. Test results indicated a much higher endurance limit for the NFC-coated balls compared to that of uncoated balls.