Abstract: An annular friction seal device to be disposed around the impeller of a turbine or high pressure compressor is disclosed. The turbine or compressor is of the type comprising, from the periphery inward, a support-ring surrounding the impeller, a first air-permeable annular layer fastened to the support-ring, and a second annular layer joined to the first layer and coming into immediate proximity with the impeller blade ends, and being abaradable by these ends. To simplify production of the annular seal device, it is provided with two annular layers provided within a single superalloy seal ring with channels bored through the entire seal ring. The channels are open to air in one zone and are closed in at least the upstream end of the other zone.