Turbine Bucket Tip Cap Using Precipitation Hardened Material
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Solution Overview
Problem
Gas turbines face reduced strength and increased maintenance due to high temperatures, which lead to swelling or creep in turbine components, particularly at the tip of the buckets, affecting thermodynamic efficiency and requiring additional cooling systems or costly manufacturing techniques.
Innovation Solution
A turbine bucket design featuring a tip cap made from precipitation hardened material with passages aligned with internal ribs, allowing precise welding and improved structural integrity, using materials like Rene N5 and GTD-111, which enhances strength and reduces creep.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If nickel or cobalt alloys are used in turbine buckets, then ductility and ease of welding are improved, but strength decreases at higher temperatures leading to swelling or creep
Solution Approach 1:
The turbine bucket is constructed as a composite structure combining nickel or cobalt alloy materials with precipitation hardened materials. The precipitation hardened material is positioned at the tip and leading/trailing edges where high temperature strength is most critical, while the nickel or cobalt alloy provides ductility and weldability in other portions of the bucket. This composite approach allows the turbine to operate at higher temperatures without excessive creep while maintaining ease of welding for assembly.
2Strength
If precipitation hardened superalloys are used in turbine components, then strength at higher temperatures is improved, but ductility decreases and welding becomes difficult
Solution Approach 1:
The precipitation hardened material is applied locally only to portions of the turbine bucket where high temperature strength is most critical, specifically the tip cap and areas subject to highest thermal stress. This localized application provides the necessary creep resistance at hot spots while leaving other portions of the bucket made from more weldable nickel or cobalt alloys, thus reducing overall welding difficulty while maintaining high temperature performance where needed.
3Strength
If additional cooling systems are added to limit maximum temperature, then component strength is maintained, but thermodynamic efficiency decreases
Solution Approach 1:
The invention changes the material parameter by incorporating precipitation hardened materials with superior high-temperature creep resistance into the turbine bucket design. This material parameter change allows the turbine to operate at higher combustion temperatures without excessive swelling or creep, thereby increasing thermodynamic efficiency. The passages aligned with internal ribs facilitate controlled thermal management through the enhanced material rather than requiring extensive external cooling systems that would extract energy from the working fluid.
4Temperature
If directional solidification and improved heat treatments are used, then turbine components can operate at higher temperatures, but manufacturing time and cost increase
Solution Approach 1:
The turbine bucket uses a composite construction combining conventional nickel or cobalt alloys with precipitation hardened materials. This composite approach allows the use of standard manufacturing processes for the majority of the bucket components, reducing manufacturing complexity and cost. The precipitation hardened material can be applied as a separate component (tip cap) that is welded to the main bucket, avoiding the need for complex directional solidification of the entire bucket while still achieving high-temperature capability at critical locations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design increases the intervals between maintenance cycles and improves thermodynamic efficiency by maintaining structural integrity at higher temperatures, reducing the need for additional cooling systems and costly manufacturing techniques.
Implementation Method 1
The tip cap includes a precipitation hardened material... These superalloys have improved strength at higher temperatures, reducing the onset of swelling or creep at operating temperatures during the life of the components.
Data Source
AI summary
A turbine bucket that includes a pressure side, a suction side opposite the pressure side, and a rib extending between the pressure side and the suction side. A tip cap is attached to the pressure side and the suction side and covers the rib. The tip cap includes a precipitation hardened material and a passage aligned with the rib. A method for assembling a turbine bucket having a pressure side and a suction side and a rib extending between the pressure side and suction side. The method includes receiving a tip cap made from a precipitation hardened material and having a passage in the tip cap. The method further includes locating the rib visually through the passage and aligning the passage with the rib. The method also includes welding the tip cap to the turbine bucket and to the rib.