Key takeaways
- The documented N45H specimen used a stated 0.35% Tb treatment. HcJ increased from 17.67 to 26.55 kOe, about 50%.
- In that specimen, Br changed from 13.62 to 13.61 kGs and BHmax from 45.42 to 45.40 MGOe. Br was essentially unchanged at the reported precision.
- A separate historical 50H composition example lists Dy at 1.2% and 0.3%, a 75% reduction in Dy. The matched validation report was not supplied; this is not the N45H experiment or a total-HREE saving.
- Diffusion distance is measured from treated surfaces. A large face dimension alone does not determine whether the core can be treated.
- Grade, chemistry, through-thickness performance and cost require part-specific confirmation.
Overview
Overview
Bulk alloying introduces material during alloy preparation. GBD treats a sintered magnet through selected surfaces, with diffusion along grain boundaries and enrichment near grain surfaces. Results depend on the starting alloy, treatment and geometry. The measured N45H case and the separate 50H composition statement support different conclusions and must remain separate.
Side-by-side
Side-by-Side Comparison
Reference properties and design questions. A count of comparison points does not establish a material or supplier recommendation.
| Criterion | Grain Boundary Diffusion (GBD) | Bulk Alloyed NdFeB |
|---|---|---|
| Process | Surface treatment and post-sinter diffusion | Alloy preparation followed by pressing and sintering |
| Geometry check | Distance from treated faces to the least-treated region | Validate the full production route for the part |
| Hot coercivity | Verify through-thickness material properties | Verify material properties for the selected alloy |
| Remanence | Measure before and after the selected treatment | Measure the proposed alloy at the working temperature |
| HREE use | Compare actual composition and material usage | Compare actual composition and material usage |
| Cost | Include diffusion, yield and qualification | Include alloy, yield and qualification |
| Available grade and geometry | Confirmed for the selected route | Confirmed for the selected route |
Confirm source conditions and the actual part requirements before using reference values as acceptance limits.
Use cases
Conditions for considering each option
When Grain Boundary Diffusion (GBD) wins
- The treated part meets through-thickness coercivity and hot working-point requirements.
- Measured material usage or part cost supports the selected diffusion route.
When Bulk Alloyed NdFeB wins
- The qualified bulk-alloyed route meets the full part specification.
- Diffusion from the available surfaces does not achieve the required internal properties.
How to choose
Decision Framework
Decision framework
Identify the treated faces and longest relevant diffusion path, then validate material properties through the section. A 50 × 20 × 3 mm plate is not rejected merely because its face dimensions exceed 10 mm. Compare hot curves, composition, yield and quotations for the actual part. The historical 50H example is one reported composition record and does not establish the result for another grade or part.
Specs
Related NdFeB Grades
N42SH
150°C classN42SH reference: 40–43 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N45SH
150°C classN45SH reference: 43–46 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N48SH
150°C classN48SH reference: 45–48 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N42UH
180°C classN42UH reference: 40–43 MGOe at 20°C, with a nominal 180°C temperature class.
Reference; drawing review required
N45UH
180°C classN45UH reference: 43–46 MGOe at 20°C, with a nominal 180°C temperature class.
Reference; drawing review required
N42EH
200°C classN42EH reference: 40–43 MGOe at 20°C, with a nominal 200°C temperature class.
Reference; drawing review required
Industries
Related Applications
EV Motors
NdFeB magnet design inputs for permanent-magnet traction motors, auxiliary drives and e-axles.
Robotics
NdFeB design inputs for robot joint motors, compact actuators and servo drives.
Industrial Automation
NdFeB magnets for stepper motors, servo drives, linear actuators, magnetic couplings, and factory automation equipment across European and North American manufacturing.
Questions
Frequently Asked Questions
How much Dy or Tb does GBD save?
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The saving is process-specific. A separate historical 50H formulation comparison lists Dy at 1.2% versus 0.3%, a 75% Dy reduction, without the requested matched validation report. It does not establish total-HREE savings, equal performance, or savings for the measured N45H specimen.
Is there a universal thickness limit for GBD?
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No limit is established here. Evaluate diffusion from the treated faces and verify coercivity in the least-treated region. The largest dimension on the drawing may be unrelated to the diffusion path.
What does the N45H specimen show?
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With a stated 0.35% Tb treatment, HcJ rose from 17.67 to 26.55 kOe. Br was 13.62 before and 13.61 kGs after treatment; BHmax was 45.42 and 45.40 MGOe. This is one recorded specimen, not a production-lot or motor-performance guarantee.
Is GBD always cheaper?
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No. Compare material usage, processing, yield and qualification costs in current quotations. A measured coercivity improvement alone does not establish a landed-cost saving.
Does GBD establish export clearance?
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No. Confirm the actual composition, item classification and transaction. A process name or reduced Dy content does not by itself determine licensing.
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