Is space expanding within superclusters of galaxies?
Not at present.
Whatever the force is that is causing the universe to expand is not yet affecting any galaxies, clustered or not. That is simply because the galaxy's inherent gravity is enough to keep it in its present state.
At some point in the extremely distant future, some scientists predict, as the universe has accelerated to a point where no galaxy is visible from any other galaxy and the universe is expanding every quickly, whatever that force is will tug at the galaxies' gravity and cause them to expand until they no longer exist.
In the end, it is speculated that this expansion will even pull apart atoms.