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SmCo Magnets
Aerospace, Defense & Energy Grade • Sintered Series 1:5 & 2:17 Rare Earth Alloys
Samarium Cobalt Magnets (SmCo Permanent Rare Earth Magnets)
CMS Magnetics is a precision manufacturer and master distributor of high-reliability Samarium Cobalt (SmCo) magnets engineered specifically for mission-critical flight hardware, guided defense platforms, and downhole energy exploration. While neodymium suffers severe flux degradation and irreversible losses past 176°F (80°C), sintered SmCo alloys provide linear demagnetization curves and zero-degas vacuum stability at continuous operational thresholds up to 572°F (300°C) (custom T350 grades rated to 662°F / 350°C). Certified for compliance with MIL-I-45208A, ITAR, and DFARS, we stock and custom-fabricate both Series 1:5 (SmCo5) and high-coercivity Series 2:17 (Sm2Co17) configurations ready for lot-traced deployment from our Garland, Texas facility.
Thermal Integrity: Usable continuous duty to 572°F (300°C); Curie threshold between 800°C–850°C.
Downhole Corrosion Proof: Negligible free iron; impervious to H2S, brine, hydrocarbons, and organic acids unplated.
Radiation & Cryo Resilient: Immune to gamma/neutron flux degradation; stable from 4 Kelvin up to 350°C.
Engineering & Defense Reference • Material Specifications & Environmental Survivability
Technical Specification Guide: Samarium Cobalt (SmCo) Rare Earth Alloys for Critical Systems
In extreme aerospace turbomachinery, guided munition fin actuators, traveling-wave tube (TWT) amplifiers, and downhole Measurement-While-Drilling (MWD/LWD) telemetry tools, component failure is catastrophic. Samarium Cobalt (SmCo) permanent magnets remain the absolute engineering standard for applications that encounter severe heat, corrosive chemicals, nuclear or space radiation, and high demagnetizing fields. By offering a reversible temperature coefficient of remanence (α(Br)) one-third that of NdFeB, SmCo preserves magnetic flux density and linear performance across temperature swings exceeding 500°F.
| Alloy Series & Grade | Remanence (Br) | Coercivity (Hcb) | Intrinsic Coercivity (Hci) | Max Energy Product (BHmax) | Max Working Temp (Tmax) |
|---|---|---|---|---|---|
| SmCo 1:5 (Grade 18) | 8.5 – 9.0 kG (0.85 – 0.90 T) | ≥ 8.0 kOe (≥ 637 kA/m) | ≥ 15.0 kOe (≥ 1194 kA/m) | 16 – 19 MGOe | 482°F (250°C) |
| SmCo 1:5 (Grade 20) | 8.8 – 9.4 kG (0.88 – 0.94 T) | ≥ 8.2 kOe (≥ 653 kA/m) | ≥ 15.0 kOe (≥ 1194 kA/m) | 19 – 21 MGOe | 482°F (250°C) |
| SmCo 2:17 (Grade 26) | 10.2 – 10.6 kG (1.02 – 1.06 T) | ≥ 9.0 kOe (≥ 716 kA/m) | ≥ 18.0 kOe (≥ 1432 kA/m) | 24 – 27 MGOe | 572°F (300°C) |
| SmCo 2:17 (Grade 30) | 10.8 – 11.4 kG (1.08 – 1.14 T) | ≥ 10.0 kOe (≥ 796 kA/m) | ≥ 20.0 kOe (≥ 1592 kA/m) | 28 – 31 MGOe | 572°F (300°C) |
| SmCo 2:17 (Grade 32) | 11.3 – 11.7 kG (1.13 – 1.17 T) | ≥ 10.2 kOe (≥ 812 kA/m) | ≥ 20.0 kOe (≥ 1592 kA/m) | 30 – 33 MGOe | 572°F (300°C) |
| SmCo 2:17 Ultra-Temp (T350) | 9.8 – 10.4 kG (0.98 – 1.04 T) | ≥ 8.5 kOe (≥ 676 kA/m) | ≥ 25.0 kOe (≥ 1990 kA/m) | 23 – 26 MGOe | 662°F (350°C) |
Stoichiometry & Metallurgy: Series 1:5 (SmCo5) vs. Series 2:17 (Sm2Co17)
Series 1:5 (SmCo5) • Sensor & Medical Focus
Composed of roughly 36% Samarium and balance Cobalt. While exhibiting lower energy products (16–21 MGOe), Series 1:5 requires lower magnetizing field thresholds (Hk ≈ 20 to 30 kOe to saturate), making it far easier to calibrate and polarize in high-precision aerospace gyroscopes, accelerometer sensors, and downhole Hall-effect sensing packages. Working threshold: 482°F (250°C).
Series 2:17 (Sm2Co17) • High Power & Propulsion Focus
Alloyed with Samarium, Cobalt, Iron, Copper, and Zirconium (Sm2(Co, Fe, Cu, Zr)17). This composition optimizes remanence and energy products up to 33 MGOe with intrinsic coercivity exceeding 25 kOe. Series 2:17 provides maximum mechanical torque density in aircraft starter-generators, magnetic bearings, and extreme-depth drilling assemblies up to 572°F / 300°C (custom 350°C).
Harsh Environment Survivability: Temperature, Downhole Fluids & Radiation
- Downhole MWD/LWD Drilling Endurance: Geothermal and deep-well drilling environments subject tools to intense vibration and bottom-hole temperatures exceeding 350°F. SmCo exhibits near-linear remanence loss without the abrupt "knee" demagnetization that causes neodymium sensors to drop telemetry signals.
- Chemical Inertness Without Plating: Because SmCo alloys contain less than 15% iron (and Series 1:5 contains zero free iron), they will not rust, decrepitate, or exfoliate when exposed to downhole brine, sour gas (H2S), crude hydrocarbons, or aviation hydraulic fluids (Skydrol). Sintered SmCo is routinely installed unplated (bare metal) in fluid-immersed sub-assemblies.
- Low Thermal Drift: SmCo retains an industry-lowest reversible temperature coefficient of remanence of −0.030% to −0.040% per °C. In precision military radar or navigation sensors, calibration remains accurate across continuous thermal cycles.
- Curie Temperature Stability: Curie points between 1,472°F and 1,562°F (800°C – 850°C) ensure complete safety against metallurgical structure changes during thermal runaways.
- Space Vacuum & Radiation Hardening: Fully inorganic sintered SmCo generates zero outgassing in high-vacuum space flight (10−9 Torr) and withstands high gamma, proton, and neutron radiation flux that embrittles and demagnetizes standard NdFeB and bonded materials.
Aerospace Fabrication Realities: Wire-EDM & Structural Substrate Bonding
Like all sintered intermetallics, Samarium Cobalt is mechanically brittle with low fracture toughness (KIC ≈ 1.5 to 2.5 MPa·m1/2). Standard high-speed steel (HSS) or carbide drilling and milling are prohibited, as point-contact friction generates micro-fissuring, thermal shock, and pyrophoric alloy swarf. CMS Magnetics fabricates complex steps, radial segments, and counterbores utilizing industrial multi-axis wire-EDM, wet diamond surface grinding, and core ultrasonic drilling with precision tolerances down to ±0.001" (±0.025 mm).
For assembly into high-nickel superalloy sleeves (such as Inconel 718, Hastelloy, or 316L stainless steel carriers), we recommend pairing structural acrylics (e.g., Loctite AA 324 with Loctite SF 7387 activator) or Mil-Spec heat-cure epoxies. To prevent localized stress concentrations during thermal expansion differential cycles, bondline gaps must be maintained at an engineered 0.003" to 0.005" (75–125 μm) using solid glass spacer beads.
Quality Assurance: 3-Axis Vector Flux & Helmholtz Verification
To meet aerospace flight-critical standards and military compliance (MIL-I-45208A), CMS Magnetics verifies production lots using calibrated 3-axis Helmholtz coils and multi-channel fluxmeters. We provide comprehensive empirical testing reports, including total magnetic dipole moment (M), magnetic flux (Φ), and magnetic angular alignment verification (≤ 1° deviation) to prevent parasitic torque in precision resolvers and turbine tachometers.
Handling Protocol for High-Energy SmCo Alloys
Fracture & High-Velocity Shrapnel Risk: Because SmCo has high magnetic attraction coupled with high brittleness, uncontrolled snapping against ferrous steel or adjacent magnets causes projectile shattering. Assembly personnel must wear ANSI-rated protective eye shields and gloves. Separate magnets using brass or polymer sliding wedges.
Implanted Medical Devices: Static magnetic fields trigger telemetry test modes in cardiac pacemakers, ICDs, and neurostimulators. Maintain a minimum safe distance of 12 inches (30 cm) from assemblies.
Looking for Alternative Alloys or Custom Defense Engineering?
If thermal exposure remains under 176°F (80°C) and raw holding force per dollar is the primary metric, browse our stock of high-grade Neodymium Rare Earth Magnets (N35–N52). For cost-effective commercial shop fixturing up to 400°F, view our Ceramic Ferrite Magnets. For ITAR compliance, custom wire-EDM slicing, or complex magnetic circuit modeling, request a formal quote through our Custom Magnet Manufacturing portal in Garland, Texas.
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