O-ring that wears through hard chrome?

A. Greg, I've had experience with plastic and rubber parts wearing grooves into hardened steel before. It's an adhesive wear mechanism, caused by the "appetite", if you will, that iron and carbon have for each other. I've not seen it happen on hard chrome to the extent you describe, but the theoretical explanation would be the same: chromium and carbon readily form chromium carbide.

Then again, it could also be an abrasive wear mechanism, if the EPR is glass or hard mineral filled. Is that possible?

Oddly enough, we've found a rougher surface, like the kind generated by shot peening, to be effective in mitigating the adhesive wear phenomenon. Of course, that kind of defeats the reason you'd use an O-ring seal in the first place...

Good luck!

A. Just as water drops can eat through solid rock if given enough time. I would review the seal design and give it enough contact area to let a lubricating film form between both surfaces.

A. Dear Greg,
you have not mentioned the rpm at which the part rotates or is it stationery. I presume it is rotating hence the groove. The o-ring has more contact surface area thus creating more heat/friction and hence the wear. check if the o-ring has an oil sealing function, if yes try using a hydraulic seal or a u-seal. The seals have less contact area hence do not damage the rotating parts. We faced a similar situation and the suggestion I gave you worked.
All the best,