Patent ID: 6962483

Claim:
A monolithic rotor formed by machining a rotor forging, the monolithic rotor comprising first and second rotor regions axially aligned within the monolithic rotor and a transition zone therebetween, the first and second rotor regions being formed of different alloys and the transition zone having a composition that differs from and varies between the first and second rotor regions, the first rotor region being located within a high pressure region of the monolithic rotor and formed from an alloy chosen from the group consisting of CrMoV low alloy steels, martensitic stainless steels containing about 11 to about 14 weight percent chromium, Fe—Ni alloys, and nickel-base alloys, and the second rotor region being located within a low pressure region of the monolithic rotor and formed from an alloy chosen from the group consisting of NiCrMoV low alloy steels and martensitic stainless steels containing about 11 to about 14 weight percent chromium, wherein the first rotor region is limited to being formed of a martensitic stainless steel, a Fe—Ni alloy, or a nickel-base alloy if the second rotor region is formed of a NiCrMoV low alloy steel.