How does fretting wear manifest at the contact points of multi-turn wave springs?

Fretting wear occurs at the interfaces where wave crests meet in a Crest-to-Crest spring or where turns overlap in a nested spring. Under high-frequency, low-amplitude vibration, the localized contact pressure and microscopic relative motion remove the protective oxide layer of the stainless steel, leading to abrasive wear and 'fretting corrosion' (often seen as a reddish or black powder). This reduces the material thickness $t$, which dramatically lowers the load capacity ($P ∝ t^3$) and creates stress risers that lead to fatigue. Lubrication with dry-film molybdenum disulfide or specifying harder coatings can mitigate this in dynamic applications.