Wear Calculation for Hard-Soft Gear Pairings Depending on Surface Hardness and Roughness

In large gear drives, through-hardened ring gears or internal gears are often in contact with case-hardened pinions. This offers economic advantages, but involves an increased risk of wear during its operation. Various test methods exist to evaluate the expected wear of the used gear-lubricant-system, but typically with case-hardened gears only. A direct transfer of the test results to the application in field is not known so far. In this study, influences from different surface hardness and surface roughness values as well as lubricating conditions were systematically investigated on a FZG back-to-back test rig. The results prove a higher risk for strong wear for hard-soft gear pairings. Based on these results, a calculation method for the wear lifetime of gears was extended to allow an estimation of the wear lifetime of gear pairings with different surface hardness based on standard wear tests.