What is the effect of bore surface roughness on the longevity of a wave spring?

Wave springs expand and contract radially during every cycle. If the bore surface roughness $R_a$ is high (e.g., $>125 μin$), the outer diameter of the spring will experience abrasive wear. This thinning of the radial wall $b$ reduces the spring rate according to $K ∝ b$. Furthermore, the friction increases the operating temperature, which can accelerate relaxation in materials like SAE 1070. For high-cycle applications (e.g., $>10^6$ cycles), the bore should be honed to a finish of $32 μin$ or better. In aerospace fuel pumps, where $17-7PH$ springs are used, the bore is often hard-anodized or coated with a dry film lubricant to minimize this friction and prevent the generation of metallic wear debris that could clog the system.