A wheel disk assembly having a wheel disk, a plurality of blade devices, which are arranged thereon in a manner distributed over the circumference, and a plurality of sealing plates, which are retained in two annular grooves spaced apart from each other radially. In this assembly, the first annular groove is provided in the wheel disk and is bounded axially outward by an annular projection. The projection, in turn, is interrupted by a recess extending in the circumferential direction, with the result that a sealing plate can be inserted axially through the recess between the annular grooves. A closure piece is furthermore provided for closing the recess, which closure piece is captively retained on the sealing plate by a form fit.