AGMA 15FTM24 PDF

Diamond-like carbon (DLC) tribological coatings have demonstrated the ability to provide gear and bearing performance enhancements in an initially narrow but increasing range of applications. These experiences have heightened awareness and curiosity in industry about the potential of DLC coatings to enhance the performance of gear train systems. Valuable benefits may include reducing the probability of micropitting wear and increasing scuffing resistance, perhaps even to enable improved oil-out performance in aerospace applications. The application of these coatings may be used to increase gearbox efficiency, not by reducing friction within tooth contacts, but by increasing tooth surface durability to allow for less viscous lubricants and reduced lubricant quantities.

It is generally known that extreme contact pressure and sliding velocity operating conditions can lead to coating wear. However, a better understanding of the thresholds that constrain coating durability and usefulness are needed so that gear and bearing engineers can more accurately specify and predict system life. This paper reports the results of testing a tungsten carbide-reinforced diamond-like carbon coating (W-DLC) as applied to AISI 4320 and AMS6308 gear materials using a rotating ball-on-disk tribology test rig under a range of conditions that simulate the contact stresses and sliding velocities of gears.