You can't expect to get away with plays like this in a freeroll. There are a lot of players who, once they have decided they like a hand, are going to see it all the through, or at least see the flop. Also, they HATE seeing people buy the pot, and they love to snap off bluffs. You should make this same play with a hand like TT and let him call you with his A9.

I wouldn't start getting pushy in a freeroll until you are on the bubble and you have identified the players who are just trying to make the money. Then you can attack their blinds. Until then, play tight and let the fish pay off your big hands.