Repairing cooling fans.

Can anyone advise me on if its possible to repair 110v Nidec/Muffin cooling fans.
I have 10 of the 4-5 inch ones that were given 220 volts by mistake.
Now whe I connect to 110 they just emit a Buzzing noise, and fan locks up like an electronic brake.
All the bearings etc are good, and they are expensive to replace and seem shame to trash them.
Anyone ever dismantle this type of fan?
any ideas
Stan

The small fans that Iv'e repaired were always dust in the bearings.

The armature may have become magnitized or the enamel insulation on the wire may have been compromised.

Are they induction motors, or do they have a start-up capacitor? If the capacitor has failed the syptoms you describe would be exactly the same. Try flicking the blades with a pencil or something similar in the direction of rotation while power is applied, if the motor is good it should rotate. The 240v may have taken the capacitor out. Hope this helps.