Can Iron Man defeat Hulk?Can he? Yes.
Has he in recent history? No, but he was going to but he was sabotaged.
Actually, there have been multiple confrontations between these two. First that comes to mind is the Original Sin where Tony (Iron Man) was on the run from the hulk and could not defeat him with a city of weapons at his arsenal. This one went completely in the favor of the Hulk. But there have been also multipe occasions where Iron Man outsmarts the Hulk, hince, the old pen is mightier than the sword.
In terms of raw physical power Iron Man could never be stronger than the hulk, in terms brain power - most of the time Tony is smarter than the hulk.