In This Article
Key Takeaways
- ◆GBD can change coercivity by introducing a diffusion source through treated surfaces.
- ◆The reported N45H case used 0.35% Tb surface coating: Hcj 17.67 to 26.55 kOe, Br 13.62 to 13.61 kGs.
- ◆The 75% Dy reduction belongs to a separate historical 50H example, from 1.2 to 0.3 on the same stated basis.
- ◆These records do not establish total-HREE or finished-price savings, or every grade and geometry.
- ◆Classify the actual composition and transaction; a diffusion process does not establish export clearance.
What the process changes
Grain boundary diffusion treats sintered material with a diffusion source and heat treatment. The response depends on composition, microstructure and processing. Avoid treating the grain interior as universally pure or unchanged. Compare magnetic properties before and after treatment on the actual candidate.
The reported magnetic comparison
The reported N45H comparison used a 0.35% Tb surface coating and reached N45UH-level coercivity: Hcj 17.67 to 26.55 kOe, Br 13.62 to 13.61 kGs and BHmax 45.42 to 45.40 MGOe. Hcj rose about 50% while rounded Br and BHmax were essentially unchanged. A separate historical 50H example reports Dy from 1.2 to 0.3 on the same stated basis, a 75% reduction.
It is a different example, not a current 50H supply offer. The records do not establish combined total-HREE savings or finished-part price savings; a full validation report remains unavailable.
Keep Dy arithmetic separate
The historical 50H example gives 1.2 before and 0.3 after on the same stated Dy basis. The reduction is (1.2−0.3)/1.2 = 75%. It is not the N45H/Tb magnetic test. Do not combine these records to calculate total heavy-rare-earth use or a finished-price percentage. The historical grade is not a current Mainrich offer.
Qualify the geometry
Diffusion distance runs inward from the treated surfaces. A large face dimension is not necessarily the controlling diffusion path. Confirm treated faces, thickness along the path and the property distribution. A rule that any dimension over 10 mm leaves an untreated core is insufficient. Qualify the proposed material and process together, especially for Ce-containing alloys.
Compare complete parts
Request hot demagnetization curves, irreversible-loss testing and finished dimensions for the proposed process. Include diffusion material, heat treatment, machining, yield and inspection in the quotation. An improvement on one material does not prove a universal BHmax increase, a fixed cost benefit or a reason to specify GBD for every high-temperature part.
Supply and export scope
Mainrich’s sintered NdFeB range is N30 to N56, with no AH grades. The top grade depends on the temperature series: N56, N54M, N52H, N52SH, N50UH and N45EH. Grades up to N52SH can be made without a Chinese export licence, so we offer those first; UH and EH grades need a licence, applied for per order.
Confirm the grade, suffix, geometry and production route for each drawing. This summary does not offer every combination; grades outside it in educational examples are not Mainrich supply offers. Grade suffixes and F/N/D series labels do not establish composition or export clearance. Classify the actual item and transaction with the exporter, including the parties, end use and route. See the export-control guide.
Frequently Asked Questions
What did the N45H comparison show?
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The reported N45H comparison used a 0.35% Tb surface coating and reached N45UH-level coercivity: Hcj 17.67 to 26.55 kOe, Br 13.62 to 13.61 kGs and BHmax 45.42 to 45.40 MGOe. Hcj rose about 50% while rounded Br and BHmax were essentially unchanged. A separate historical 50H example reports Dy from 1.2 to 0.3 on the same stated basis, a 75% reduction. It is a different example, not a current 50H supply offer. The records do not establish combined total-HREE savings or finished-part price savings; a full validation report remains unavailable.
Where does the 75% Dy reduction come from?
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The historical 50H example gives 1.2 before and 0.3 after on the same stated Dy basis. The reduction is (1.2−0.3)/1.2 = 75%. It is not the N45H/Tb magnetic test. Do not combine these records to calculate total heavy-rare-earth use or a finished-price percentage. The historical grade is not a current Mainrich offer.
Does GBD always reduce finished cost?
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Request hot demagnetization curves, irreversible-loss testing and finished dimensions for the proposed process. Include diffusion material, heat treatment, machining, yield and inspection in the quotation. An improvement on one material does not prove a universal BHmax increase, a fixed cost benefit or a reason to specify GBD for every high-temperature part.
Does GBD establish export clearance?
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Grade suffixes and F/N/D series labels do not establish composition or export clearance. Classify the actual item and transaction with the exporter, including the parties, end use and route. See the export-control guide.
Does a large face dimension rule out diffusion?
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Diffusion distance runs inward from the treated surfaces. A large face dimension is not necessarily the controlling diffusion path. Confirm treated faces, thickness along the path and the property distribution. A rule that any dimension over 10 mm leaves an untreated core is insufficient. Qualify the proposed material and process together, especially for Ce-containing alloys.
Can I order every listed grade with diffusion?
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Mainrich’s sintered NdFeB range is N30 to N56, with no AH grades. The top grade depends on the temperature series: N56, N54M, N52H, N52SH, N50UH and N45EH. Grades up to N52SH can be made without a Chinese export licence, so we offer those first; UH and EH grades need a licence, applied for per order. Confirm the grade, suffix, geometry and production route for each drawing. This summary does not offer every combination; grades outside it in educational examples are not Mainrich supply offers.
Send the drawing, hot magnetic requirements and annual volume to compare a proposed diffusion route with the existing material.
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