Graded Composite Transition Joint for Dissimilar Metal Weld Cracking
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Solution Overview
Problem
Advanced ultra-supercritical (A-USC) power plants face challenges with materials and manufacturing technologies, particularly in dissimilar metal weldments (DMWs), which experience severe service conditions including fireside coal-ash corrosion/erosion, steam side oxidation, creep strength, thermal fatigue strength, and weldability issues.
Innovation Solution
The development of additively manufactured, graded composite transition joints (AM-GCTJs) that utilize a grating or lattice pattern with a graduated density, transitioning from one alloy to another, and subjected to hot isostatic pressing (HIP) to densify the composite, thereby creating a smooth graded transition that mitigates thermal stresses and CTE mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If dissimilar metal weldments are used in A-USC power plants, then the system can operate at high temperature and pressure, but the weldments experience severe thermal stresses and CTE mismatch leading to cracking and thermal creep fatigue
Solution Approach 1:
The patent applies local quality by creating a graded composite transition joint where the material composition varies continuously from one alloy to another through a gradient structure. This gradual transition in material properties (particularly CTE and strength) at the interface reduces thermal stresses and prevents cracking, while still enabling operation at high temperatures up to 760°C.
Solution Approach 2:
The patent uses composite materials by combining two different alloys (Alloy A and Alloy B) in a graded transition joint configuration. The composite structure integrates materials with different thermal and mechanical properties, allowing the system to withstand high temperature and pressure conditions while mitigating the harmful effects of CTE mismatch through the intermediate gradient zone.
2Ease of manufacture
If conventional manufacturing methods are used for transition joints, then the production process is simple, but the joints exhibit stress concentrations and premature failures under cyclic operating conditions
Solution Approach 1:
The patent applies parameter changes by systematically varying the material composition parameter along the transition joint from one alloy to another. This continuous parameter change creates a gradient structure that eliminates abrupt property changes, reducing stress concentrations and improving thermal creep fatigue resistance while maintaining manufacturability through controlled deposition processes.
Solution Approach 2:
The patent applies dynamics by creating a dynamic, non-uniform material composition that adapts to the varying stress and temperature conditions across the joint interface. The graded structure allows the material properties to change continuously, providing optimal performance at each location rather than using a static, uniform composition throughout.
3Ease of manufacture
If a uniform alloy composition is used throughout the joint, then the manufacturing process is straightforward, but the joint cannot accommodate differences in thermal expansion between dissimilar metals
Solution Approach 1:
The patent applies local quality by tailoring the material composition at each location within the transition joint to match the local requirements. The graded structure provides different material properties at different positions, with the composition varying continuously to accommodate the CTE mismatch between the two dissimilar metals, while still using a relatively straightforward manufacturing process.
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
AM-GCTJs enhance the cracking and thermal creep fatigue resistances of DMWs, reduce stress concentrations, and provide a cost-effective remedy for premature failures under cyclic operating conditions, enabling safe and economical operation in A-USC power plants.
Implementation Method 1
subjecting the composite to hot isostatic pressing (HIP) to densify the composite
Implementation Method 2
the preparing includes preparing the grating or lattice pattern by at least one of selective laser melting (SLM) or selective laser sintering (SLS)
Data Source
AI summary
A method for producing an additively manufactured, graded composite transition joint (AM-GCTJ) includes preparing a grating or lattice pattern from a first alloy A; the grating or lattice pattern includes pores in the grating or lattice patterns. The grating pattern is built from a first end to a second end being denser on the first end than on second end, and gradually reduces density by increasing the pore size and/or reducing density of the grating or lattice pattern; adding a second alloy B powder to the second end of grating or lattice pattern. The second alloy B powder is filled towards the first end. A composite is formed of first alloy A and second alloy B powder in the AM-GCTJ. The composite is subjected to hot isostatic pressing (HIP) to densify the composite. The second alloy B is graduated from the first end to the second end O of AM-GCTJ.