Extending useful life of a cobalt-based gas turbine component
AssigneeALSTOM Technology Ltd
InventorsWarren Miglietti, John Roderick
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Abstract
A method of extending the useable life of a gas turbine component fabricated from a cobalt-based alloy is disclosed. The method includes applying a rejuvenation process to the alloy where the alloy is placed in a protected atmosphere and heated to three different elevated temperatures and held at the elevated temperatures for approximately four hours each. Application of the rejuvenation process allows gas turbine components to be returned to service for at least one more service interval of approximately 24,000 operating hours.
Claims8
A method of extending a useable life of a cobalt-based gas turbine component comprising:
- cleaning the gas turbine component;
- filling cracks in the gas turbine component with a braze material;
- heating the component in a protected atmosphere to a first holding temperature range of 800° F.-1000° F. for approximately 30 minutes;
- heating the component in the protected atmosphere to a second holding temperature range of 1800° F.-2000° F. for approximately 45 minutes, wherein heating the component to the second holding temperature range is preceded directly by a first heat cycle having the first holding temperature range and a ramp up period from the first holding temperature range to the second holding temperature range;
- dissolving carbides agglomerated on the component to limit the carbides from forming crack initiation sites by heating the component in the protected atmosphere a third holding temperature range of to 2200° F.-2250° F. for approximately 30 minutes to 4 hours, wherein heating the component to the third holding temperature range is preceded directly by a second heat cycle having the second holding temperature range and a ramp up period from the second holding temperature range to the third holding temperature range;
- reducing heat to the component in the protected atmosphere to a fourth holding temperature range of 2000° F. to 2200° F. for approximately 4 hours to approximately 24 hours, wherein reducing heat to the fourth holding temperature range is preceded directly by a third heat cycle having the third holding temperature range and a ramp down period from the third holding temperature range to the fourth holding temperature range.
A method of extending a useable life of a cobalt-based gas turbine component comprising:
- cleaning the gas turbine component, wherein cleaning comprises removing one or more of oxides, nitrides, and sulphides from cracks in the gas turbine component;
- filling the cracks in the gas turbine component with a braze material;
- burning binders from the braze material by heating the component in a protected atmosphere to a first holding temperature range of 800° F.-900° F. for approximately 30 minutes;
- stabilizing the component below a solidus temperature of the braze material by heating the component in the protected atmosphere to a second holding temperature range of 1800° F.-1900° F. for approximately 45 minutes;
- dissolving clusters of M23C6 carbides on the component by heating the component in the protected atmosphere to a third holding temperature range of 2200° F.-2250° F. for approximately 30 minutes to 4 hours to limit the M23C6 carbides from forming crack initiation sites;
- and
- forming a microstructure in the component by reducing heat to the component in the protected atmosphere to a fourth holding temperature range of 2100° F. to 2200° F. for approximately 4 hours to approximately 24 hours, wherein the microstructure includes an ideal structure and distribution of intermetallic phases, wherein reducing heat to the fourth holding temperature range is preceded directly by a ramp down period from the third holding temperature range to the fourth holding temperature range.
Dependencies are inferred from the claim text.