Official Answer
Answer
The contact points of a wave spring (the peaks) slide slightly against the mating surface as the spring is compressed. If the mating surface is too rough ($Ra > 63 \mu in$), the spring peaks will experience abrasive wear, reducing the material thickness $t$ and lowering the load capacity over time ($P \propto t^3$). Conversely, if the surface is too smooth, 'stiction' can occur. For high-cycle applications, a surface finish of $16-32 \mu in Ra$ is ideal. Hardened mating surfaces (e.g., case-hardened steel) are preferred to prevent the spring from 'brinelling' or creating indentations, which would alter the effective work height and load.
