Sintered Preform Diffusion Brazing for High-Temperature Component Holes
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Solution Overview
Problem
Existing methods for filling and closing blind holes, through-holes, and cavities in high-temperature components like gas turbine buckets and nozzles face challenges such as inconsistent application, porosity, and poor mechanical properties due to the use of pliable braze materials like pastes, putties, and tapes, and limitations with welding techniques that can lead to cracking and inaccessibility.
Innovation Solution
A process using sintered preforms made from a mixture of base alloy and melting point depressant powders, compacted and sintered to form a rigid preform that can be tailored in size and shape to fit specific openings, allowing for high-density diffusion brazing with improved mechanical properties and the ability to include self-locking and cooling features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pliable braze materials (pastes, putties, slurries, tapes) are used to fill openings, then the braze material can be easily applied and conforms to the opening shape, but the resulting brazement has low density, excessive porosity and voids, and poor mechanical properties
Solution Approach 1:
The invention changes the physical state parameter of the braze material from pliable (paste, putty, slurry, tape) to rigid (preform). This parameter change resolves the contradiction by providing a material that maintains its shape for easy application while achieving high density and low porosity for improved mechanical properties.
Solution Approach 2:
The invention uses a composite braze material comprising metal particles (such as nickel, cobalt, or iron-base superalloy particles) combined with a binder. This composite structure provides both the rigidity needed for precise placement and the bonding capability for strong mechanical properties, resolving the contradiction between ease of application and mechanical strength.
2Area of stationary object
If pliable braze materials are used to fill large openings, then the material can potentially cover the area, but the material flows away from the brazing area due to its pliability
Solution Approach 1:
The invention changes the physical state parameter of the braze material from pliable to rigid. This allows the material to maintain its shape and be precisely positioned in large openings without flowing away, while still achieving complete coverage and accurate placement.
3Reliability
If welding techniques (TIG, electron beam, laser beam) are used to close holes, then the holes can be sealed, but the localized heat energy produces fusion zones and heat affected zones prone to liquation and strain age cracking
Solution Approach 1:
The invention replaces the welding process (which uses localized heat energy to melt and fuse materials) with a diffusion brazing process. The rigid preform is diffusion bonded to the substrate at temperatures below the melting point of the base metal, eliminating the fusion zone and heat affected zone that are prone to cracking, while still achieving reliable sealing.
Solution Approach 2:
The invention changes the temperature parameter of the joining process by using diffusion brazing at temperatures below the melting point of the base metal, as opposed to welding which requires temperatures at or above the melting point. This parameter change eliminates the harmful thermal effects that cause cracking while maintaining sealing effectiveness.
4Reliability
If welding is used to fill holes from casting operations, then the holes can be closed, but welding is not practical due to costs, poor fusion weldability of the material, inaccessibility with welding equipment, and other restrictions
Solution Approach 1:
The invention replaces the welding process with a diffusion brazing process using a rigid preform. This substitution eliminates the need for complex welding equipment and skilled operators, making the process more accessible and cost-effective while achieving reliable hole closure even in inaccessible 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 process achieves consistent, high-density brazements with improved mechanical properties and reduced porosity, overcoming the limitations of pliable braze materials and welding techniques, enabling effective sealing and enhancement of high-temperature components.
Implementation Method 1
The powder mixture is combined with a binder and compacted to form a compacted preform, which is then heated to remove the binder and form a rigid sintered preform.
Implementation Method 2
the sintered preform is placed in the opening and diffusion braze bonded within the opening to form a brazement comprising the particles of the base alloy dispersed in a matrix formed by the second alloy
Data Source
AI summary
A process for filling openings, including blind holes, through-holes, and cavities, in high temperature components. The process entails forming a powder mixture by mixing particles of at least a base alloy and a second alloy that contains a sufficient amount of a melting point depressant to have a lower melting temperature than the base alloy. The powder mixture is combined with a binder and compacted to form a compacted preform, which is then heated to remove the binder and form a rigid sintered preform. The sintered preform is produced, or optionally is further shaped, to have a cross-sectional shape and dimensions to achieve a clearance of up to 200 micrometers with the opening, after which the preform is placed in the opening and diffusion bonded within the opening to form a brazement comprising the particles of the base alloy dispersed in a matrix formed by the second alloy.