MIM-316L Stainless Steel
MIM-316L is an austenitic stainless steel widely used in Metal Injection Molding (MIM) for applications requiring superior corrosion resistance. Containing 2-3% molybdenum per ASTM A240, it outperforms standard 304-grade stainless steel in chloride environments, making it ideal for medical devices, marine components, and chemical processing equipment.
At Emitech, we specialize in producing precision MIM-316L parts with tight tolerances (±0.3% to ±0.5%) and excellent surface finishes. Our advanced MIM process ensures near-full density and consistent mechanical properties across complex geometries that would be difficult or impossible to achieve with conventional machining.
MIM 316L Stainless Steel Data
| Grade | Chemical Composition | Sintering Temperature (°C) | Density (g/cm³) | Yield Strength | Hardness | ASTM Specification | Typical Applications |
|---|---|---|---|---|---|---|---|
| 316L | Fe/Cr16-18/Ni10-14/Mo2-3 | 1,325–1,375 | 7.9 | ≥205 MPa | 70–90 HRB / 120–180 HV | ASTM F138, MPIF 35 | Medical devices, marine hardware, food equipment |
Material Characteristics
MIM-316L retains all the benefits of wrought 316 stainless steel while enabling the production of intricate, net-shape components. Key characteristics include:
- Excellent corrosion resistance — Especially in chloride and acidic environments due to molybdenum content
- Non-magnetic — Austenitic structure remains non-magnetic after sintering
- High strength and ductility — Tensile strength up to 520 MPa with 30% elongation
- Good weldability — Suitable for post-sintering welding if required
- Biocompatible — Meets requirements for surgical instruments and temporary implants
- Polishable to mirror finish — Ideal for decorative and hygienic applications
Chemical Composition
The typical chemical composition of MIM-316L powder conforms to ASTM F138 and MPIF Standard 35:
| Element | Weight % (min-max) |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 16.0 - 18.0 |
| Nickel (Ni) | 10.0 - 14.0 |
| Molybdenum (Mo) | 2.0 - 3.0 |
| Carbon (C) | ≤ 0.03 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.03 |
Physical & Mechanical Properties
| Property | Value |
|---|---|
| Density (sintered) | ≥ 7.8 g/cm³ |
| Tensile Strength | ≥ 520 MPa |
| Yield Strength | ≥ 205 MPa |
| Elongation | ≥ 30% |
| Hardness (HV) | 120 - 180 |
| Young's Modulus | 193 GPa |
| Thermal Expansion | 16.0 μm/m·K (20-100°C) |
| Max Service Temperature | 800°C (intermittent) |
MIM-316L vs MIM-304 Comparison
While both are austenitic stainless steels, the addition of molybdenum in 316 creates significant performance differences:
| Feature | MIM-316L | MIM-304 |
|---|---|---|
| Corrosion Resistance | Superior (marine/chemical) | Good (general purpose) |
| Mo Content | 2.0 - 3.0% | None |
| Chloride Resistance | Excellent | Moderate |
| Cost | Higher | Lower |
| Magnetic Response | Non-magnetic | Non-magnetic |
| Typical Applications | Medical, marine, chemical | Food equipment, general industrial |
Typical Applications
MIM-316L is the material of choice when corrosion resistance and biocompatibility are critical:
- Medical devices — Surgical instruments, instrument handles, endoscopic components, dental brackets
- Marine hardware — Fasteners, connectors, and fittings exposed to seawater
- Chemical processing — Valve components, pump housings, sensor housings
- Food & pharmaceutical — Equipment parts requiring frequent sterilization and cleaning
- Automotive — Fuel system components, exhaust sensor housings
- Electronics — EMI shielding enclosures, connector bodies
Why Choose Emitech for MIM-316L Parts?
- 20+ years of MIM manufacturing experience
- In-house tooling design and production (15-20 day lead time)
- Tight tolerances maintained across complex geometries
- Full traceability from powder lot to finished part
- Secondary operations available: CNC machining, polishing, passivation, electropolishing
- ISO 9001 certified quality management system
Frequently Asked Questions
Q: Is MIM-316L suitable for permanent medical implants?
A: MIM-316L (ASTM F138) is approved for surgical instruments and temporary implants. For permanent implants, ASTM F75 (Co-Cr-Mo) or titanium alloys like Ti-6Al-4V are typically preferred. We manufacture all these materials — contact us for guidance on material selection.
Q: What is the difference between MIM-316 and MIM-316L?
A: MIM-316L is the low-carbon variant (≤0.03% C vs ≤0.08% C in standard 316). The lower carbon content minimizes sensitization and intergranular corrosion during welding. For most MIM applications, 316L is recommended if post-sintering welding is required.
Q: Can MIM-316L parts be polished to a mirror finish?
A: Yes. MIM-316L achieves excellent surface finishes (Ra 0.8-1.6 μm as-sintered) and can be further polished to mirror quality through vibratory finishing, electropolishing, or manual polishing. This makes it ideal for decorative and hygienic applications.
Q: What is the maximum operating temperature for MIM-316L parts?
A: MIM-316L can withstand continuous service temperatures up to 870°C, but for optimal mechanical properties, we recommend keeping applications below 800°C. Above this range, carbide precipitation may reduce corrosion resistance.
Q: How does MIM-316L compare to 17-4 PH stainless steel in MIM?
A: 17-4 PH offers significantly higher strength (up to 1310 MPa when aged) but is magnetic and has inferior corrosion resistance compared to 316. Choose 316 when corrosion resistance and non-magnetic properties are priority; choose 17-4 PH when maximum strength is required.
Q: What surface treatments are available for MIM-316L?
A: Common treatments include passivation (ASTM A967), electropolishing, bead blasting, PVD coating, and electroless nickel plating. Passivation is highly recommended to restore the passive oxide layer after any post-processing.
Q: What is the typical shrinkage rate for MIM-316L during sintering?
A: MIM-316L typically exhibits an isotropic shrinkage of 15-20% during sintering. Our tooling design accounts for this shrinkage with precision shrinkage compensation to ensure final dimensions meet specification.
Q: What is the minimum wall thickness for MIM-316L parts?
A: We can achieve wall thicknesses as thin as 0.3 mm for MIM-316L, though 0.5 mm is recommended for optimal mechanical properties and processing reliability. Thinner walls may be possible depending on part geometry and production volume.
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References
- ASTM A240/A240M-23, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip, ASTM International, 2023.
- MPIF Standard 35, Materials Standards for MIM 316L, 2020 Edition.
- ASTM F138-19, Standard Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for Surgical Implants, ASTM International, 2019.