Improving the surface durability of wind gears via shot peening and superfinishing

Gearbox power density plays a key role in wind energy competitiveness. As wind turbines have become increasingly larger, gear surface durability and flank fracture load carrying capacity have become key elements in gearbox sizing. While shot peening and superfinishing have been studied independently as potential techniques to improve surface durability, few reported studies have combined both of these processes to increase the gear flank load-carrying capacity. In this work, spot pitting tests were carried out to evaluate the expected load-carrying capacity increase for wind gears through this combination of finishing processes. The results are consistent with previous research's conclusions and highlight the need for further investigations to evaluate potential increased flank fracture risk related to the near-surface residual stress distribution. • Shot peening has been introduced frequently as a technique to increase gears bending capacity, but its application to gear flanks, followed by superfinishing, is not yet considered in standards. • In small gears, the combination of shot peening and superfinishing allows a pitting capacity increase that can be calculated through extended factors. For large gears, shot peening does not affect the pitting behavior significantly. • The combination of shot peening and superfinishing can be considered an appropriate gear recovery technique for local defects, if the gear is properly prepared. • Inducing residual compressive stresses via peening on the gear surface has the collateral effect of generating reduced compressive residual stresses inside the part.