Novel Surface Modification Treatment of Wind Turbine Gearbox Components for Resistance to Extreme Environments

New products and services are needed to improve the performance and durability of wind turbine mechanical-drive systems that operate in extreme environments. In particular, the gearbox components (gears and bearings) require wide-temperature-range operation; resistance to corrosion; and solid-lubrication capability for start/stop, run-in, and lubrication starvation events. In this project, these requirements will be addressed by developing and demonstrating a novel, surface modification treatment for wind turbine gearbox components, which will enhance system reliability and result in more efficient renewable energy generation sources. The surface modification treatment will consist of: (1) High Intensity Plasma Ion Nitriding (HIPIN) of gear steels to increase the load-carrying-capability/hardness of subsurface gear regions; (2) Plasma-Enhanced Magnetron Sputtering (PEMS) to deposit thick, nearly defect-free, dense nitride coatings for corrosion barrier properties and hardness/durability; and (3) doped solid-lubricating coatings (diamondlike carbon (DLC) or Mo/W disulfide) to provide low friction and low wear rates for gear run-in, start/stop operations, and periods of insufficient liquid lubrication. Phase I will design the surface modification treatment for the most-common gear steels used in wind-turbine gearbox components; apply the aforementioned HIPIN PEMS and doping processes for surface treatment; and perform systematic tests to determine the coating composition, indent adhesion, hardness, residual stress, and tribological performance (load-bearing capability, coefficient of friction, wear factor, high-speed reciprocating sliding performance). Commercial Applications and other Benefits as described by the awardee: The surface modification technology should have application anywhere gears and bearings are used in gearboxes and transmissions. Commercial markets have been estimatead at over $15 billion, and include the transportation, utility, power generation, agriculture/farming, aeronautical, and aerospace industries. In addition, the military would benefit from increased performance envelopes and longer lifetimes of components for helicopter gearboxes and mechanical assemblies (e.g., lift fan gearbox) for tactical fighters.