Cocrmo Material Properties

CoCrMo (Cobalt-Chromium-Molybdenum) material properties are characterized by an exceptional combination of high stiffness (Young’s Modulus ~210–240 GPa), superior corrosion resistance, and excellent biocompatibility. This alloy is widely regarded as the gold standard for load-bearing medical implants and high-performance engineering components due to its ability to withstand harsh environments without degrading. Here are the key mechanical and physical properties of CoCrMo:

• Elastic Modulus (Stiffness): 210 – 240 GPa (Significantly stiffer than Titanium).
• Ultimate Tensile Strength (UTS): 655 – 1280 MPa (Depending on whether it is Cast ASTM F75 or Wrought ASTM F1537).
• Yield Strength: 450 – 840 MPa.
• Density: Approximately 8.3 – 8.4 g/cm³.
• Wear Resistance: Exceptional, derived from a hard carbide microstructure dispersed in a cobalt matrix.
• Corrosion Resistance: Superior protection through the spontaneous formation of a passive Chromium-Oxide (Cr2O3) film.
• Biocompatibility: Non-toxic and non-irritant, minimizing immune response in the human body.

Mechanical Stiffness And Elastic Modulus

One of the most decisive properties of CoCrMo is its extremely high elastic modulus (Young’s modulus). Its value is between 210 – 240 GPa, which is significantly “harder” than other medical alloys such as titanium alloys we commonly use.

This high stiffness is essential for applications that require rigidity and minimal deformation under heavy loads. In the design of weight-bearing medical implants, this feature ensures that the component can maintain its shape and structural integrity even under the high mechanical stress of the daily movement of the human body.

Ultimate Tensile Strength (UTS) And Manufacturing Standards

It must be said that the strength performance of CoCrMo largely depends on its processing method. Its ultimate tensile strength (UTS) span is very large, ranging from 655 to 1280 MPa. This difference is completely determined by industry standards:

• Cast CoCrMo (ASTM F75): Strength is usually at the low end of the range, but it is very cost-effective for manufacturing parts with complex shapes.
• Forged CoCrMo (ASTM F1537): Due to its forged and thermomechanical treatment, it exhibits excellent strength (up to 1280 MPa), which makes it an ideal choice for the most demanding high-performance engineering components.

In addition, the yield strength of 450 – 840 MPa ensures that the material can withstand considerable external forces before any permanent plastic deformation occurs.

Excellent Wear Resistance Based On Microstructure

For any material used for joint replacement or sports engineering components, wear resistance is a “life or death” indicator. CoCrMo achieves excellent wear resistance due to its unique microstructure.

This alloy consists of hard carbides dispersed in a cobalt matrix. From a metallographic point of view, these carbides act as reinforcing phases, protecting the surface of the material from wear and sliding wear. This makes CoCrMo particularly good in “metal-on-metal” or “gold-on-polyethylene” joint applications, where long-term durability is not negotiable.

Excellent Corrosion Resistance

When discussing the material properties of CoCrMo, its resistance to degradation in harsh environments is a top priority. This alloy provides superior protection by 1 a chemical mechanism called “passivation.

Once exposed to oxygen, CoCrMo spontaneously forms a thin, stable and passive chromium oxide (Cr2O3) film on its surface. This barrier effectively shields the underlying metal from chemical attack. This is critical for implants that are exposed to the corrosive environment (body fluids) of the human body for long periods of time, ensuring that the material does not rust or degrade over decades of use.

Biocompatibility And Safety

For medical applications, no matter how high the mechanical strength is, if it is not safe, it is useless. CoCrMo is highly regarded in large part because of its excellent biocompatibility.

The material has been shown to be non-toxic and non-irritating. Its chemical stability prevents the release of harmful ions that could trigger adverse reactions. As a result, it minimizes the body’s immune response, which further strengthens its position as the “gold standard” for long-term implantable devices.

Physical Density

Finally, the density of CoCrMo is around 8.3-8.4g/cm³. This physical property gives the alloy 1 a solid, heavy feel. Although it is heavier than titanium, in engineering design, this high density tends to contribute to the stability of the material and is often tied to the high strength and durability required for high load functions.

Author：Jack
“I am a technical specialist focused on high-performance medical alloys. With deep expertise in ASTM standards, I analyze critical material properties to help engineers understand the mechanics of CoCrMo implants.”