Prewet Surface Preparation for Diffusion Bonding Irregular Interfaces
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Solution Overview
Problem
Diffusion bonding of components with complex or discontinuous surfaces is challenging due to ineffective use of braze foils and contamination from traditional binders, leading to inconsistent bonding and unwanted material modifications.
Innovation Solution
A method involving the selective deposition of a binder material with controlled viscosity and mass density, followed by the application of braze powder, which is then adhered to the surface by heating, forming a prewet surface that allows for diffusion bonding without the need for excessive braze material, using a roller with specific surface roughness and in a controlled environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If braze foils are used for diffusion bonding, then bonding capability is improved, but effectiveness is reduced for irregular or discontinuous surfaces
Solution Approach 1:
The invention changes the physical state and application parameters of the braze material from foil form to powder form, allowing it to be deposited as a coating that conforms to irregular and discontinuous surfaces. The binder material with controlled viscosity enables the powder to be applied uniformly across complex geometries, resolving the contradiction between bonding reliability and adaptability to surface irregularities.
Solution Approach 2:
The invention creates a composite material system combining braze powder with a specialized binder material. This composite allows the braze material to be applied to discontinuous surfaces while maintaining bonding effectiveness, as the binder holds the powder in place on complex geometries before diffusion bonding occurs.
2Ease of manufacture
If traditional binders are used for braze powder, then deposition is facilitated, but contamination of the bonded joint occurs
Solution Approach 1:
The invention changes the chemical composition parameters of the binder material to create a specialized binder that does not contaminate the joint. The binder is formulated with specific viscosity characteristics and chemical properties that enable easy deposition while being compatible with diffusion bonding processes, eliminating contamination issues associated with traditional binders.
Solution Approach 2:
The invention extracts and removes the harmful contamination aspect from the binder material while retaining the beneficial deposition facilitation properties. The specialized binder is designed to perform only the necessary function of holding braze powder during application without introducing contaminants into the bonded joint.
3Quantity of substance
If other methods of depositing elemental or ionic materials are used, then deposition is achieved, but unwanted modifications of adjacent surfaces occur
Solution Approach 1:
The invention introduces a specialized binder material as an intermediary between the braze powder and the substrate surface. This binder acts as a mediating layer that facilitates powder deposition without directly modifying the adjacent surfaces, allowing material deposition while preventing unwanted surface modifications that would occur with direct deposition methods.
Solution Approach 2:
The binder material serves as a temporary, disposable carrier that facilitates powder deposition during the process but is subsequently removed or consumed without leaving harmful residues. The binder performs its function of holding and transferring the braze material, then disappears through decomposition or evaporation without permanently modifying the substrate surfaces.
4Area of stationary object
If braze powder is applied to discontinuous surfaces, then coverage is improved, but consistent deposition becomes difficult or impossible
Solution Approach 1:
The invention changes the viscosity parameter of the binder material to a specific range that enables consistent flow and deposition characteristics. This controlled viscosity allows the binder-powder mixture to uniformly coat discontinuous surfaces, achieving both comprehensive coverage and consistent deposition thickness that would be impossible with traditional application methods.
Solution Approach 2:
The specialized binder material provides multiple functions simultaneously: it adheres braze powder to the surface, maintains consistent deposition across varying geometries, and enables uniform coverage on discontinuous surfaces. This multi-functional binder resolves the contradiction between achieving broad coverage and maintaining deposition consistency.
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
This method enables consistent and robust diffusion bonding of complex surfaces with reduced contamination and material property modifications, resulting in a monolithic component with a homogeneous bonded interface suitable for high-temperature applications like gas turbine engines.
Implementation Method 1
contacting a binder material with a discontinuous surface comprising surface regions separated by gaps, the binder material being selectively deposited onto the surface regions and having a viscosity in a range from 0.05 Pa.s (50 cP) to 30 Pa.s (30,000 cP) to form a self-supporting layer without flowing into the gaps
Implementation Method 2
A method involving the selective deposition of a binder material with controlled viscosity and mass density, followed by the application of braze powder, which is then adhered to the surface by heating, forming a prewet surface
Implementation Method 3
Removing the binder material may comprise pyrolyzing or vaporizing the binder material
Implementation Method 4
Removing the binder material may comprise pyrolyzing or vaporizing the binder material
Implementation Method 5
The discontinuous surface may be heated to a temperature at or above a sintering temperature of the braze powder and below a melting temperature of the braze powder
Implementation Method 6
Diffusion bonding is a solid-state bonding method, where elevated temperatures and typically high pressures are employed to obtain diffusion of atoms between mating components, allowing for formation of a thermally-stable metallurgical bond
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E~1F
AI summary
A method of preparing a surface for diffusion bonding comprises contacting a binder material with a discontinuous surface comprising surface regions separated by gaps. The binder material is selectively deposited onto the surface regions and has a sufficient viscosity to form a self-supporting layer without flowing into the gaps. The self-supporting layer of binder material comprises a mass density in a range from about 1.55 g/m2 (0.001 g/in2) to about 77.50 g/m2 (0.050 g/in2). A braze powder is distributed over the self-supporting layer of binder material, and a predetermined amount of the braze powder is attached to the binder material. The discontinuous surface is then heated to remove the binder material and adhere the braze powder to the discontinuous surface. Thus, a prewet surface with a braze deposit thereon is formed.