scope:

Micropitting is a surface fatigue phenomenon on highly loaded case hardened gear flanks. Main contributors are local stress, surface roughness, sliding speed and lube oil properties. To determine the lube oil performance with respect to micropitting, different test methods have been established in the past. Actual proposals are evaluated for adopting suitable calculation methods for micropitting resistance to the ISO 6336 gear rating standards. But is micropitting necessarily a damage in any case? Practical experience shows, that a certain level of micropitting is actually acceptable, leading to even more favorable load distribution and can end up in a stable flank condition performing without problems for the designed service live. The paper describes testing, calculation approaches and application to practical cases with respect to micropitting on wind turbine and high speed gears and perennial observations and experience.