What was found
(CAN) WHILE INFLIGHT, AT APPROXIMATELY FL320, THE CREW REPORTED HIGH ENGINE VIBRATIONS ON THE NR 2 ENGINE. THEY REDUCED POWER ON THE ENGINE TO IDLE TO REDUCE/STOP THE ENGINE VIBRATIONS. THEY DECLARED A PAN PAN EMERGENCY AND RETURNED TO WHERE THEY LANDED OVERWEIGHT BY APPROX 3000-4000K. ALSO, DURING THE RETURN, THE CREW DISCOVERED THEY WERE UNABLE TO CROSSFEED THE FUEL AND THEY LANDED WITH A FUEL IMBALANCE THAT WAS CLOSE TO BUT NOT EXCEEDING FUEL IMBALANCE LIMITS. AFTER LANDING THE CREW INSPECTED THE ENGINE AND FOUND DAMAGE TO SEVERAL BLADES AND THE ENGINE CONE MISSING WITH APPARENT DAMAGE, FURTHER INTO THE ENGINE.