The Development of Hydrogen-free DLC-coated Valve-lifter

Due to its lower friction property, a hydrogen-free diamond-like carbon coating (DLC) obtained by an ion-plating physical vapor deposition (PVD) process as an amorphous carbon film (a-C) was applied to an engine valve lifter to reduce mechanical losses. The effect of the a-C coating on reducing friction was evaluated with an engine motoring tester using actual engine parts. To meet the specifications of the valve lifter, a study was made of the typical topography of the a-C coating surface profile and the effect of the film thickness against abrasive wear.