Recess Braze Joint Cooling to Prevent Porosity and Hot Cracking
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Solution Overview
Problem
Conventional braze processes for metal alloys, particularly in high-stress applications like rotary machines, often result in solidification defects such as porosity and hot cracking due to differential cooling and solidification shrinkage, reducing the tensile strength and creep life of braze joints.
Innovation Solution
A system and method that includes a component with a recess and a cap of braze material, where a thermal insulation layer covers the exposed braze surface and a cooling system extracts heat from the base closer to the inner edge than the cap, controlling the cooling rate to minimize solidification defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional braze processes are used to repair cracks or defects in metal alloys, then the component can be restored, but solidification defects such as porosity and hot cracking occur due to differential cooling and solidification shrinkage, reducing tensile strength and creep life
Solution Approach 1:
The patent applies parameter changes by modifying the cooling rate parameters during the braze process. Specifically, it uses a two-stage cooling approach: initial rapid cooling to room temperature followed by controlled slow cooling to a temperature above the solidus point, then rapid cooling again. This dynamic parameter change resolves the contradiction by preventing solidification defects while maintaining braze joint integrity.
Solution Approach 2:
The patent implements periodic action through cyclic cooling processes. The braze material undergoes repeated heating and cooling cycles, including rapid cooling to room temperature, slow cooling to above-solidus temperatures, and final rapid cooling. This periodic thermal treatment eliminates porosity and hot cracking by controlling solidification behavior at different stages, thereby improving manufacturing precision without sacrificing reliability.
2Manufacturing precision
If the gap filled with braze material is greater than 0.1 mm, then porosity is likely to form, but if the gap is less than 0.1 mm, then hot cracking is likely to occur
Solution Approach 1:
The patent applies dynamics by making the cooling rate adaptive rather than static. The cooling process dynamically adjusts its rate based on the temperature stage: rapid cooling initially, then slow cooling when approaching the solidus point, and finally rapid cooling again. This dynamic control allows the system to handle various gap sizes (both >0.1mm and <0.1mm) effectively, preventing both porosity and hot cracking by optimizing the cooling behavior at each stage.
3Manufacturing precision
If the braze material closer to the surface cools faster than the braze material deeper into the defect, then solidification defects occur, but if uniform cooling is achieved, then the braze joint quality improves
Solution Approach 1:
The patent applies preliminary action by performing rapid cooling to room temperature first, which establishes a uniform temperature baseline throughout the braze material before the final slow cooling and reheating stages. This preliminary rapid cooling prevents temperature gradients from developing during subsequent heating and cooling cycles, ensuring uniform cooling behavior and eliminating conditions that would lead to solidification defects, thereby improving both manufacturing precision and reliability.
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 approach reduces or eliminates solidification defects in the braze joint, enhancing the tensile strength and creep life, and extending the service life of components in high-stress environments.
Implementation Method 1
an insulation layer that at least partially covers the exposed braze surface
Implementation Method 2
a cooling system extracts heat from the base closer to the inner edge than the cap
Implementation Method 3
heating the braze material within an environment to create at least partially molten braze material
Data Source
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AI summary
The present application relates to a system (300) for creating a braze joint (202). The system (300) includes an environment (206) operable to reach a braze temperature sufficient to melt at least a portion of a braze material (218). The system (300) also includes a component (204) within the environment (206), the component (204) including a base (210) having a base surface (212), a recess (214) depending from the base surface (212) into the base (210) to an inner edge (224), and the braze material (218) within the recess (214) and forming a cap (220) above the base surface (212). The braze material (218) fills the recess (214) from the cap (220) to the inner edge (224). The cap (220) has an exposed braze surface (222). The system (300) also includes an insulation layer (302) that at least partially covers the exposed braze surface (222). The present application relates also to a method of brazing the recess (214) defined within the base (210).