All parts can benifit from cryotreating. The earlier the part is treated, the better.

As stated before, cryotreating cannot fix micro stress cracks that have already begun, but it can slow down the rate of further cracking.

Ideally, the part should be cryotreated before any machining is done on it.

So to answer this question, you can cryogenically treat used parts, but you will not see the same amount of benifit as you would, if the rotors had been treated when they were new.

__________________
George Carstens