Evaluation of DLC coatings for spark-ignited, direct-injected fuel systems

The suitability of diamond-like carbon (DLC) coatings for reduction of friction and wear in spark-ignited, direct-injected fuel systems has been investigated. Three commercially available DLC coatings have been compared to near-frictionless carbon (NFC) coatings and to uncoated metal in standardized lubricity tests and custom wear tests intended to simulate the fuel system environment. The coatings were applied to both laboratory balls and flats and to production fuel injector tips. These coatings provided improvements in friction and wear over uncoated surfaces, with the greatest improvements found in parts coated with NFC.