CASE STUDY · MOTOR APPLICATIONS
Heavy Rare Earth Content Cut from 3% to Under 0.6%
A motor OEM using high-temperature NdFeB magnets in lawn mower motors was facing unsustainable cost pressure as heavy rare earth prices spiked to ¥2,000/kg. After 2 years of R&D, our grain boundary diffusion process cut unit cost by 5–10% while preserving full H-grade performance.
5–10%
Unit Cost Reduction
<0.6%
Heavy Rare Earth
3M+
Motors in 2021
THE CHALLENGE
Rare Earth Price Spike Threatens Margin and Orders
Our client — a motor OEM — manufactures high-volume motors for lawn mower applications. The motors require high-temperature grade NdFeB magnets (H-grade and above) that maintain magnetic performance under sustained heat exposure during operation.
Conventionally, producing high-temperature NdFeB blanks with H-grade or higher ratings requires adding 3% or more of heavy rare earth elements — specifically Dysprosium (Dy) or Terbium (Tb) — into the base alloy. The exact proportion varies by grade, but the cost impact is significant: heavy rare earth prices surged to ¥2,000/kg (approximately $275/kg), making these materials a dominant cost driver in the final magnet price.
The client's end customers refused to accept price increases. At the same time, the OEM could not downgrade to a lower magnetic grade without compromising motor performance. The result: shrinking margins, reduced orders, and a serious competitive disadvantage in an increasingly cost-sensitive market.
THE INITIAL APPROACH
Conventional Process: 3%+ Heavy Rare Earth, Unsustainable Cost
In the early development phase, producing high-temperature magnets (H-grade and above) through conventional sintering required adding more than 3% Dy or Tb directly into the NdFeB alloy during powder preparation. While this achieved the required coercivity for thermal stability, it created two problems:
- Cost: Heavy rare earth elements accounted for a disproportionate share of raw material cost, and price volatility made quoting nearly impossible
- Supply risk: Heavy rare earth supply is concentrated and subject to export controls, creating long-term procurement risk
The client demanded a price reduction — but required all magnetic parameters to remain unchanged. A fundamentally different manufacturing approach was needed.
Conventional vs. Grain Boundary Diffusion Process
Before — Conventional Sintering
After — Grain Boundary Diffusion
THE SOLUTION
Grain Boundary Diffusion: 2 Years of R&D to Production
Over a 2-year period of iterative experimentation, Mainrich developed and validated a grain boundary diffusion (GBD) process specifically optimized for this application. Instead of mixing heavy rare earth elements throughout the entire magnet alloy, GBD selectively diffuses Terbium (Tb) along the grain boundaries of a sintered NdFeB blank — precisely where it's needed to enhance coercivity.
The result: the same H-grade magnetic performance is achieved with less than 0.6% heavy rare earth content — an 80%+ reduction compared to the conventional 3%+ process. Since the Tb is concentrated at grain boundaries rather than diluted throughout the bulk material, every atom does more work.
This process required careful control of diffusion temperature profiles, surface coating uniformity, and post-diffusion heat treatment. Each parameter was optimized through hundreds of test batches before the process was qualified for volume production.
Development Timeline
Phase 1 — Lab Validation
Initial GBD experiments on H-grade blanks. Proved that coercivity targets could be met with <1% Tb content. Identified optimal diffusion temperature range.
Phase 2 — Process Optimization
Refined Tb surface coating methods, diffusion time/temperature profiles, and post-diffusion annealing. Hundreds of test batches to achieve consistent results across different magnet geometries.
Phase 3 — Customer Qualification
Client motor testing with GBD magnets. All magnetic parameters (Br, Hcj, BHmax) met original H-grade specifications. Thermal cycling and accelerated aging tests passed.
Phase 4 — Volume Production
Full-scale production launched. Unit price reduced 5–10% versus conventional process. Client's motor project reached 3 million units in 2021.
TECHNICAL ADVANTAGE
Why Grain Boundary Diffusion Works
| Parameter | Grain Boundary Diffusion | Conventional Bulk Addition |
|---|---|---|
| Heavy RE content | <0.6% | 3%+ Dy or Tb |
| Coercivity (Hcj) | Equivalent — H-grade maintained | H-grade baseline |
| Remanence (Br) | Higher — less RE dilution | Slightly reduced by RE |
| Raw material cost | 5–10% lower | Baseline |
| Supply chain resilience | 80% less RE dependency | Fully exposed to RE pricing |
THE RESULT
3 Million Motors. 10% Cost Savings. Next Target: <0.3% RE.
The client was extremely satisfied with the results. Motor testing was highly successful — all H-grade performance specifications were met with no compromise. The client's lawn mower motor project scaled to over 3 million units produced in 2021.
Beyond the immediate cost savings, this project delivered strategic value: by reducing heavy rare earth usage by more than 80%, both Mainrich and the client reduced their exposure to rare earth price volatility and supply disruption — a growing concern across the motor industry.
Looking ahead, as competition intensifies, we are working on the next generation of the process: achieving high-temperature performance (200°C+) through a direct-press method combined with advanced diffusion techniques — with a target of reducing heavy rare earth content to below 0.3%.
3%→0.6%
Heavy rare earth reduction
3M+
Motors produced in 2021
<0.3%
Next-gen RE target
“When heavy rare earth prices spiked, we thought we'd have to sacrifice performance or lose the contract. Mainrich spent two years developing a diffusion process that gave us the same H-grade specs at 10% less cost — and with 80% less rare earth dependency. That's not just a cost saving, it's a strategic advantage.”— Motor Division Engineer, Lawn Mower OEM
WHAT'S NEXT
Next Target: <0.3% RE for 200°C+ Applications
As cost competition intensifies across the motor industry, Mainrich is developing the next generation of high-temperature NdFeB magnets. The goal: achieve 200°C+ thermal stability through a direct-press sintering method — without compromising any performance parameters — combined with an advanced grain boundary diffusion process that reduces heavy rare earth content to below 0.3%.
This represents a further 50% reduction from our current GBD process, pushing the boundaries of what's achievable in rare earth efficiency for high-temperature magnet applications.
Facing Rare Earth Cost Pressure?
Our grain boundary diffusion process can reduce heavy rare earth content by 80%+ while maintaining full magnetic performance. Send us your current grade specs — we'll assess feasibility and quote within 48 hours.