A gas turbine rotor blade and rotor disk arrangement is provided. The rotor blade and the rotor disk includes a coating in order to seal the gap which normally exists between the bottom part of the blade root and the bottom part of the disk slot. The coating may be applied to the blade root or to the disk itself on the bottom part of the disk slot. The coating is preferably an abradable nickel-alloy Bentonite coating. The coating may also be applied to only a portion of the areas being sealed, omitting a portion at the start of the slot or at the start of one of the lobes of the blade root, so that a lead-in is formed, whereby the blade can more easily be inserted into the slot.