CoCr28 Introduction
Cobalt-chromium-molybdenum alloy (CoCr28) is a nickel-free, cobalt-based alloy composed of 28% chromium, 4% molybdenum, and the balance cobalt. It is a material used in many applications as a biocompatible corrosion-resistant alloy. It is also known as an orthopedic or surgical alloy, and is mostly used in the form of implants such as spinal fusion cages and hip replacement components.
A Brief History of CoCr28
CoCr28 is the most modern and versatile form of cobalt alloy, claimed to have been invented in 1975. It has the ability to respond to the body’s chemistry, providing superior strength and superior corrosion resistance. Its properties differentiate it from stainless steel and other traditional implants, making it the preferred choice for medical and dental applications.
Composition and Properties of CoCr28
The composition of CoCr28 consists of 28 percent chromium, 4 percent molybdenum, and the balance being cobalt. It is usually alloyed with other elements like niobium, niobium-titanium, and vanadium in certain concentrations. The addition of these other elements helps to control the hardness, strength, and impact resistance of the finished parts.
CoCr28 alloy has excellent mechanical properties, making it suitable for both load-bearing and non-load bearing applications. It is one of the most wear-resistant alloys available, providing superior resistance to corrosion, even in highly corrosive environments. It is this corrosion resistance that makes CoCr28 ideal for orthopedic and dental implants.
Its ability to form a hard oxide layer provides superior oxidation resistance and also protects it from corrosion. The oxide layer build-up over time increases the hardness, impact strength, and ductility of the alloy, and appears in brown, yellow, and black colourations.
Common Applications of CoCr28
CoCr28 is most commonly used in orthopedics, prosthetics, and implantable devices. It is also used in the aerospace and automotive industries, as well as in dental implants, dental bridges, and other dental prosthetics.
In the orthopedic field, CoCr28 is used to create spinal fusion cages and hip implants, as well as other reconstructive, orthopedic, and soft tissue implants, because of its relative flexibility and resistance to wear and fatigue.
In the aerospace and automotive industries, CoCr alloys are used for a variety of components such as gears, shafts, bolts, and pins. They are also used in the production of turbines and other high-performance engines, which need to resist corrosion and high-heat environments.
In the dental industry, CoCr28 is used to make bridges, veneers, and crowns. It is also used to fabricate dental implants and abutments, and is often the preferred choice of material due to its biocompatibility and corrosion resistance, as well as its hardness and good wear resistance.
Advantages of CoCr28
As compared to other alloys, CoCr28 has several advantages. It has a relatively low coefficient of friction and good wear resistance, making it highly biocompatible and able to resist wear and fatigue. Its corrosion resistance makes it a popular choice of material for dental and orthopedic implants. It has high strength and hardness, and is able to form a hard oxide layer that protects it from further corrosion.
Disadvantages of CoCr28
Like all alloys, CoCr28 also has some disadvantages. It has a relatively high melting point and requires a high level of heat input during fabrication and welding. It is also susceptible to hydrogen embrittlement if not treated properly, which can lead to cracking and premature failure of parts.
Conclusion
CoCr28 is a versatile and highly desirable alloy with a wide range of applications. It offers excellent mechanical properties and corrosion resistance, making it suitable for orthopedic, dental, and prosthetic applications. Its ability to form a hard oxide layer makes it resistant to corrosion and wear, while its low coefficient of friction makes it a popular choice for medical applications. Despite its advantages, CoCr28 is susceptible to hydrogen embrittlement, so it should be treated carefully during fabrication and welding.
