Three Blue Orbs

An urn contains 2 red orbs and 1 blue orb. Each step you draw an orb uniformly at random and then replace the drawn orb with a blue orb (so the urn always holds 3 orbs, and a drawn blue orb is replaced by a blue orb).

What is the expected number of draws until all orbs in the urn are blue? Give an exact fraction or decimal.