Hard chrome plating solution effect on cadmium plated part

The part will need to be masked either way, in all probability. Chrome plating solution will attack the cad far faster than the cyanide cad will attack the chrome, so I would try the chrome first. Either way, you need to go in HOT.
If your chrome tank is much above ambient temp, I would warm the part up in a hot rinse tank before going into the chrome IF you decide to try the cad first.

I do not like the term "flash hard chrome" as hard chrome needs some thickness much higher than a flash to serve a normal hard chrome function. I will buy using a hard chrome tank to put a chrome flash on a part. Probably semantics, but once it gets into print, it can be misinterpreted by someone.

Steve,