High-reliability turbine metal sealing material

A steam turbine comprising a sealing device for reducing a fluid leaking from a gap between a stator and a rotor of the turbine, a metal sealing material being used in the sealing device,

• wherein the metal sealing material comprises a porous metal layer and the porous metal layer comprises a surface layer directly coming into contact with a working fluid and a lower layer lying thereunder,
• wherein the porosity of the surface layer is smaller than the porosity of the lower layer,
• wherein the porous metal layer comprises, as a main component, an MCrAlY alloy where M is either one of Ni and Co or both thereof, and the MCrAlY alloy comprises 15% to 30% of Cr, 6 to 15% of Al and 0.3 to 1.0% of Y, the balance comprising either one of Ni and Co or both thereof, and
• wherein a thickness of the porous metal layer is in the range of 0.3 to 3.0 mm, and a ratio of the surface layer to the lower layer is in the range of 0.1 to 1.0.