You say; are two parts involved, running on each other, an eccentric and its mate.
Having the same material for two parts running together is not really good design unless the parts are hardened and ground or otherwise finished very smooth; similar materials sliding together can gall up and seize (unless the material is brass which is the only exception I know about).
A hardenable material such as O1 could be suitable if you can correctly heat treat it.
Alternatively if you can incorporate a bushing or wear pad made out of brass or bronze for the sliding elements it may be possible to use C1018 which is a low carbon mild steel which cannot be hardened without carburizing.
An open mind is a virtue...so long as all the common sense has not leaked out.