Multi-megawatt wind turbine gearboxes operate under demanding environmental conditions including
considerable variation in temperature, wind speed, and air quality. It is not uncommon for gearboxes rated for
a maintenance free 20-year lifespan to fail after only a few years. These gearboxes experience several types
of repairable damage including micropitting or“gray staining”, abrasive wear, foreign object debris (FOD)
damage, surface corrosion and fretting corrosion. Wear is greatest on the input stage, especially on the sun
pinion gear. Historically, grinding is uilized to refurbish these damaged gears. However, there are numerous
drawbacks including but not limited to high capital investment and the extraordinary amount of time and skill
involved in the grinding process. Moreover, nitrided gears cannot be ground and must be scrapped. However,
chemically accelerated vibratory finishing, or isotropic superfinishing (ISF), represents a value adding,
low-cost option for refurbishing both case carburized and nitrided gears. lsotropic superfinishing removes
light to moderate gear flank surface damage. The result is a surface with a non-directional pattern with a
roughness of approximately 0.08 mm or less. Moreover, evidence suggests that isotropic superfinishing
imparts a finish that increases gear durability and service life in the field. A case study on a sun pinion gear is
presented.

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