Can I charge a 12V 2A NiCd battery with 18V 14.6A?
Definitely DO NOT attempt to charge your 12 volt battery with that power supply - it will do its best to get the battery voltage up to 24 volts (or whatever voltage it is set to).  The battery will probably be destroyed (perhaps violently) by the resulting high current.

You should only use a charger designed to charge 12 volt NiCD batteries to charge your battery.