Cold Spray Deposition of Brittle Magnets Without Melting
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Solution Overview
Problem
Current additive manufacturing techniques struggle to effectively deposit high-energy product permanent magnets with high coercivity and maximum energy density, particularly due to the brittleness of materials like NdFeB, which leads to significant material waste and loss of magnetic properties.
Innovation Solution
The method involves using a cold spray technique to deposit brittle magnetic particles onto a substrate, where the particles are accelerated to supersonic velocities and impact the substrate, preserving the microstructure and adhering without melting, thus maintaining the magnetic properties and achieving near-full density deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If cold spray is used to deposit brittle magnetic particles, then material waste is minimized and microstructure is preserved, but the particles do not adhere effectively due to lack of plastic deformation
Solution Approach 1:
The patent changes the physical state and mechanical properties of brittle magnetic particles by subjecting them to high-pressure torsion (HPT) processing. This transforms the particles into a ultrafine-grained state with enhanced ductility and plastic deformability, enabling them to undergo the necessary plastic deformation for effective cold spray adhesion while minimizing material waste and preserving microstructure.
2Manufacturing precision
If directed energy beams are used to melt powder for additive manufacturing, then deposition is achieved, but the desired grain structure is destroyed
Solution Approach 1:
The patent replaces thermal processing (directed energy beams that melt powder) with mechanical processing (high-pressure torsion that ultrafine-grains particles). This mechanical approach achieves particle densification and deformation necessary for deposition while preserving and even enhancing the desired grain structure, avoiding the microstructure destruction inherent in melting processes.
3Ease of manufacture
If conventional sintering and grinding processes are used for magnet manufacturing, then magnets are produced, but over 25% material is lost and the process is wasteful
Solution Approach 1:
The patent performs preliminary ultrafine-graining of the magnetic particles through high-pressure torsion before the additive manufacturing process. This pre-processing step creates particles with optimized mechanical properties for deposition, enabling near-net-shape manufacturing that minimizes subsequent machining and grinding operations, thereby reducing material loss from over 25% to minimal amounts.
4Ease of manufacture
If aluminum-NdFeB composite is used for cold spray, then spraying is enabled, but magnetic performance is severely degraded
Solution Approach 1:
The patent extracts and eliminates the aluminum binder component from the composite, using only pure brittle magnetic particles. The high-pressure torsion processing imparts the necessary ductility and deformability to these pure magnetic particles, enabling them to be sprayed effectively without requiring aluminum additives that would dilute and degrade magnetic performance.
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 approach allows for the formation of coercive magnets with high energy density and complex shapes, minimizing material waste and preserving the magnetic properties of the starting material, achieving densities close to theoretical limits.
Implementation Method 1
cold spray technique includes pressurizing a gas, heating the pressurized gas to a temperature below a melting temperature of the material, and directing a gas stream comprising the gas and a powder through an outlet of a nozzle toward a substrate for depositing the powder onto the substrate
Implementation Method 2
The plurality of particles have structural characteristics defined by an impact of the particles on the substrate and/or on previously deposited particles
Data Source
AI summary
In one aspect of an inventive concept, a product includes a substrate and a material formed from a precursor powder, where the material includes a plurality of particles from the precursor powder deposited on the substrate. The plurality of particles have structural characteristics defined by an impact of the particles on the substrate and/or on previously deposited particles. Moreover, the material has a microstructure, where the microstructure of the material is substantially the same as a microstructure of the precursor powder. The microstructure of the material is characterized by at least one property, where the at least one property is substantially the same as a corresponding at least one property of the precursor powder.