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Grain boundary diffusion / high-coercivity NdFeB

Put heavy rare earthwhere coercivity is decided.

GBD diffuses dysprosium or terbium along grain boundaries instead of mixing it through the magnet body. The route is reviewed for high-temperature motor programs that need more coercivity with controlled heavy rare-earth input.

Discuss a GBD gradeView capability matrix
N30 to N58Base grade range
H / SH / UH / EHCoercivity review
Blocks / arcs / ringsDeveloped geometries
In-houseMOFCOM handling
Real NdFeB productsFinished sintered neodymium magnets in several cylindrical sizes and coatings
Sintered NdFeB / product referenceFinished magnets shown as product evidence, with GBD route confirmed against each drawing and grade target.
Factory-verified GBD case ·  export licensing handled in-house ·  automotive IATF 16949 work runs through the network's certified plant ·  response within 1 business day
01 / THE BUYER DECISION

Coercivity at the boundary, not through the bulk.

Conventional alloying distributes Dy or Tb through the blank. GBD concentrates it along the grain boundary network, where resistance to demagnetization is established.

GBD decision ledgerConventional route / GBD route
Decision pointConventional alloyingGBD route
Where Dy or Tb goesMixed through the entire magnet blank.Diffused along the grain boundaries.
Material useHeavy rare earth is added through the bulk to reach the coercivity target.In the verified N45H to N45UH case, a 0.35% Tb surface coating delivered 75% less Dy.
Magnetic strengthBulk heavy rare earth can dilute the main magnetic phase and reduce Br.The verified case raised Hcj from 17.67 to 26.55 kOe with no Br loss.
Supply exposureMore Dy or Tb mass per part increases price and supply exposure.Lower heavy rare-earth mass per part, with the same licensing discipline.
GBD is a grade and geometry decision, not a blanket upgrade.

Mainrich reviews the thermal envelope, demagnetization margin, coating, magnet dimensions, volume, and export destination before recommending the route.

02 / VERIFIED PERFORMANCE

One measured case, four procurement facts.

The performance claim below is the factory-verified production case. It is the reference point for a new drawing review, not a universal result applied to every geometry.

Factory-verified GBD case / via a 0.35% Tb surface coating

N45H to N45UH, without the dysprosium bill.

Hcj +50%Verified coercivity increase
17.67 to 26.55 kOeMeasured Hcj result
No Br lossRemanence maintained
75% less DyReduced heavy rare-earth loading
Thermal marginGBD is evaluated when H, SH, UH, or EH coercivity is needed and bulk heavy rare-earth loading can be reduced.
Motor geometriesThe developed route covers blocks, arcs, tiles, and radial multipole rings for qualified motor programs.
Buyer documentationQuotes separate grade, diffusion route, coating, export licensing, and QC evidence.
03 / PROCESS WALK

Surface preparation to verified batch.

The process changes the grain boundary while leaving the Nd2Fe14B grain interior largely untouched. Each release still depends on geometry, heat treatment, finish, and magnetic verification.

01
Set the base magnet

Confirm grade, geometry, tolerance, coating, and operating temperature before diffusion.

02
Prepare the surface

Clean and prepare the magnet so the Dy or Tb compound can be applied consistently.

03
Apply the surface layer

Use a controlled surface layer instead of alloying heavy rare earth through the full magnet body.

04
Diffuse under heat

Vacuum heat treatment moves Dy or Tb inward along the grain boundary network.

05
Finish and verify

Complete coating, BH curve confirmation, dimensional checks, and batch records.

04 / PRODUCTION FIT

Use it where heat and demagnetization margin justify it.

GBD is most relevant to compact motors and qualification-heavy programs already calling for H, SH, UH, or EH coercivity. Final grade selection follows the motor's actual thermal and magnetic load.

Application review ledgerStarting points
ApplicationStarting gradeReview driver
Humanoid jointsN45SH / N48SH100 to 130°C internal motor temperatures
EV tractionN42SH / N45UHHigh duty cycle and demagnetization margin
Servo motorsN42H / N45SHStable torque under repeated acceleration
Wind generatorsN42SH / N45SHLong service life and supply resilience
2015
R&D started

Initial grain boundary diffusion development.

2018
Blocks in production

GBD-treated square and rectangular magnets.

2020
Arcs and tiles

Diffusion extended to motor magnet geometries.

2023
Radial rings

Multipole ring production for compact robotics motors.

RFQ NOTES

Before the grade review.

A drawing and real operating temperature make the comparison more useful than a grade name alone.

Does every high-temperature magnet need GBD?

No. GBD is reviewed when a design needs high-coercivity material and the grade, geometry, volume, and heavy rare-earth exposure justify the route.

Does GBD remove MOFCOM licensing requirements?

No. Applicable Dy- or Tb-bearing grades still require the relevant export licensing. Mainrich handles that licensing in-house.

What should be sent for a GBD review?

Send the drawing, target grade, operating temperature, coating requirement, destination, prototype quantity, and annual volume.

Put the thermal envelope on the table

Compare the GBD and conventional routes.

Send the drawing, grade target, operating temperature, coating, quantity, and destination. An engineer responds within 1 business day. Pricing follows within 2 business days.

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