Advanced Powder Products, Inc.
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Philipsburg, PA 16866
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Biocompatible alloys are essential to the success of metal injection molding (MIM) in medical and orthopedic applications.
These specialized alloy systems—particularly cobalt-chromium (CoCr) and select stainless steels—are designed to integrate seamlessly with the human body. Advanced Powder Products (APP) provides a wide variety of biocompatible MIM materials engineered for long-term implantation, optimized for both biological safety and mechanical performance.
MIM enables the production of complex, high-density metal parts with tight tolerances—making it ideal for miniature or intricate components in medical devices. Biocompatible alloys used in this process must meet stringent criteria across materials science, corrosion resistance, and mechanical behavior to ensure both functionality and patient safety.
To visualize how different MIM materials compare in terms of key properties such as tensile strength, density, and elongation, refer to the chart below titled "Biocompatible MIM Materials Comparison".
Download Spec SheetThe foremost requirement for implantable MIM components is biocompatibility. Alloys used in this application must be non-toxic, non-carcinogenic, and non-allergenic. They must also avoid triggering immune responses and support tissue integration. APP's biocompatible alloys are validated through ISO and ASTM testing standards to ensure long-term compatibility in vivo.
Cobalt-chromium (CoCr) alloys are widely used due to their excellent biocompatibility and proven track record in joint replacements and dental implants. When produced via the injection molding MIM process, CoCr components retain the same bio-inert properties while enabling near-net-shape manufacturing of complex geometries.
The human body is a chemically aggressive environment—fluids such as blood and interstitial fluid contain chloride ions that can corrode many conventional alloys. Biocompatible alloys like CoCr and 316L stainless steel resist corrosion even under prolonged exposure.
MIM-produced stainless steel alloys, particularly 316L, offer a strong balance of corrosion resistance and mechanical integrity. This makes them ideal for temporary implants and surgical instruments.
Implanted MIM components must withstand a wide range of physical demands, including cyclic loading, tensile stress, and wear. Biocompatible alloys used by APP are engineered with high strength, fatigue resistance, and wear-resistant characteristics.
To better understand the comparative strengths of these materials, see the "Typical Properties of Biocompatible Alloys" chart below, which outlines metrics like hardness, tensile strength, and elongation at break.
One of the major advantages of using metal injection molding for implantable alloys is the design freedom it offers. MIM supports:
This flexibility reduces material waste and supports high repeatability, especially important in medical devices where quality assurance is paramount.
Low alloy steels—though common in industrial MIM parts—are generally unsuitable for implant use. Their composition often lacks corrosion resistance and may introduce alloying elements that are cytotoxic or incompatible with human tissue. Stress shielding is another concern, as mismatched modulus of elasticity can cause bone resorption over time.
While low alloy steel in metal injection molding is excellent for structural or mechanical parts, it fails to meet the stringent requirements of biocompatible MIM materials.
316L stainless steel stands out as a bridge material. It is biocompatible, corrosion resistant, and well-characterized in both MIM metal injection molding and traditional machining processes. It is commonly used in dental implant hardware, orthopedic screws, and other components that require sterilizability and short-to-mid-term implantation.
While not as corrosion-resistant as CoCr, 316L remains a viable solution for a wide variety of applications—especially where cost sensitivity is a factor.
17-4 stainless steel offers higher strength than 316L but lower corrosion resistance. It is used in certain medical device housings and structural supports where long-term implantation is not required. It is not typically chosen for applications involving direct or prolonged contact with bodily fluids.
420 stainless steel provides excellent hardness and wear resistance but is limited by its corrosion performance. Like 17-4, it is often used in surgical instruments or temporary hardware rather than permanent implants. Its biocompatibility is application-dependent and should be evaluated case-by-case.
The selection of a biocompatible alloy for MIM implants must consider:
At Advanced Powder Products, our metallurgical team collaborates with device manufacturers to evaluate and select the most appropriate materials for both performance and safety.
| Grade | Hardness | Alloy Features | Applications |
|---|---|---|---|
| F-75 (ASTM F2886) | 25 HRC | High strength, superior corrosion resistance, non-magnetic, biocompatibility | Prosthetic replacements (hips, knees, etc.) bone plates, screws, rods, heart valves |
| MP35N (ASTM F562) | 8 HRC |
| F-75 (ASTM F2886) |
| Hardness |
| 25 HRC |
| Alloy Features |
| High strength, superior corrosion resistance, non-magnetic, biocompatibility |
| Applications |
| Prosthetic replacements (hips, knees, etc.), bone plates, screws, rods, heart valves |
| MP35N (ASTM F562) |
| Hardness |
| 8 HRC |
| Alloy Features |
| High strength, superior corrosion resistance, non-magnetic, biocompatibility |
| Applications |
| Prosthetic replacements (hips, knees, etc.), bone plates, screws, rods, heart valves |
| Alloy | C | Mn | Si | Cr | W | V | Ni | Mo | Co | Cu | Fe |
|---|---|---|---|---|---|---|---|---|---|---|---|
| MIM F-75 | 0.35 Max | 1.00 max | - | 27-30 | - | - | 0.50 Max | 5-7 | Bal | - | 0.75 Max |
| MIM MP35N | 0.025 Max | 0.15 Max | - | 19-21 | - | - | 33-37 | .9 - 10.5 | Bal | - | 1.00 max |
| MIM F-75 | ||
| Carbon (C) | Manganese (Mn) | Silicon (Si) |
| 0.35 max | 1.00 max | - |
| Chrome (Cr) | Tungsten (W) | Vanadium (V) |
| 27 - 30 | - | - |
| Nickel (Ni) | Molybdenum (Mo) | Cobalt (Co) |
| 0.50 max | 5 - 7 | Bal. |
| Copper (Cu) | Iron (Fe) | |
| - | 0.75 max | |
| MIM MP35N | ||
| Carbon (C) | Manganese (Mn) | Silicon (Si) |
| 0.025 max | 0.15 max | - |
| Chrome (Cr) | Tungsten (W) | Vanadium (V) |
| 19 - 21 | - | - |
| Nickel (Ni) | Molybdenum (Mo) | Cobalt (Co) |
| 33 - 37 | .9 - 10.5 | Bal. |
| Copper (Cu) | Iron (Fe) | |
| - | 1.00 max | |
| Material | Density (g/cm3) | YS (MPa) | UTS (MPa) | Elongation (%) | Unnotched Charpy impact energy (J) | Macro Hardness | Young's Modulus (GPa) |
|---|---|---|---|---|---|---|---|
| MIM F-75 - Hipped | 7.8 | 520 | 1000 | 40 | - | 25 HRC | 190 |
| MIM MP35N | 8.3 | 400 | 900 | 10 | - | 8 HRC | - |
| MIM F-75 - Hipped | |
| Density (g/cm3) | YS (MPa) |
| 7.8 | 520 |
| UTS (MPa) | Elongation (%) |
| 1000 | 40 |
| Macro Hardness | Young's Modulus (GPa) |
| - | 25 HRC |
| Unnotched Charpy Impact Energy (J) | |
| 190 | |
| MIM MP35N | |
| Density (g/cm3) | YS (MPa) |
| 8.3 | 400 |
| UTS (MPa) | Elongation (%) |
| 900 | 10 |
| Macro Hardness | Young's Modulus (GPa) |
| - | 8 HRC |
| Unnotched Charpy Impact Energy (J) | |
| - | |
| Material | YS (MPa) | UTS (MPa) | Elongation (%) | Reduction in Area (%) | Macro Hardness |
|---|---|---|---|---|---|
| MIM F-75 | 520 | 1000 | 40 | 25 | 25 HRC |
| MIM F-75 Minimum (ASTM F2886) | 480 | 825 | 10 | 10 | - |
| Cast F-75 Typical | 550 | 880 | 16 | 18 | 25-35 HRC |
| Cast F-75 Minimum | 450 | 665 | 8 | 8 | 25-35 HRC |
| MIM F-75 | |
| YS (MPa) | UTS (MPa) |
| 520 | 1000 |
| Elongation (%) | Reduction In Area (%) |
| 40 | 25 |
| Macro Hardness | |
| 25 HRC | |
| MIM F-75 Minimum (ASTM F2886) | |
| YS (MPa) | UTS (MPa) |
| 480 | 825 |
| Elongation (%) | Reduction In Area (%) |
| 10 | 10 |
| Macro Hardness | |
| - | |
| Cast F-75 Typical | |
| YS (MPa) | UTS (MPa) |
| 550 | 880 |
| Elongation (%) | Reduction In Area (%) |
| 16 | 18 |
| Macro Hardness | |
| 25-35 HRC | |
| Cast F-75 Minimum | |
| YS (MPa) | UTS (MPa) |
| 450 | 665 |
| Elongation (%) | Reduction In Area (%) |
| 8 | 8 |
| Macro Hardness | |
| 25-35 HRC | |
Donald F. Heaney, Powder Injection Molding of Implantable Grade Materials, Proceedings of MSEC:2006 ASME International Conference on Manufacturing Science and Engineering, October 8-11, 2006, Ypsilanti, MI, paper no. MSEC2006-21049.
John L. Johnson and Donald F. Heaney, Metal Injection Molding of Co-28Cr-6Mo, Medical Device Materials III , ASM, 2006.
** Handbook of Metal Injection Molding , 2nd ed. 2019. D.F. Heaney, founder and CEO of Advanced Powder Products. ISBN:9780081021521
