Cobalt-based alloy is a hard alloy that is resistant to various types of wear and corrosion as well as high-temperature oxidation. It uses cobalt as its main component and also contains a considerable amount of nickel, chromium, tungsten and a small amount of alloying elements such as molybdenum, niobium, tantalum, titanium, lanthanum, and occasionally iron. Cobalt-based alloys can be used to make welding wires, castings and forgings, etc. depending on the composition of the alloy. What we are talking about today is mainly the role of cobalt-based alloys in medicine.
Medical metal materials that are more common in life are generally used in various aspects such as surgical auxiliary equipment, artificial organs, hard tissues, soft tissues, etc., and are widely used. However, the main problem in the application of biomedical metal materials is the diffusion of metal ions into surrounding tissues due to corrosion in the physiological environment and the degradation of the properties of the implant material itself. The former may cause toxic side effects, and the latter often leads to implant failure. Medical cobalt-based alloys are widely used in the manufacture of orthopedic implants due to their two major characteristics of wear resistance and corrosion resistance. There are two basic types of medical cobalt-based alloys: cobalt-chromium-molybdenum alloys and cobalt-nickel-chromium-molybdenum alloys.
Cobalt-chromium alloy was originally used as aerospace material. Later, due to its good wear resistance, corrosion resistance and high strength, it was widely used in the articular surface components and load-bearing components of artificial joints. At the same time, due to its good biocompatibility, it is also a commonly used material for dental implants.
Cobalt-chromium-molybdenum alloy and nickel-chromium-molybdenum alloy are variants of cobalt-chromium alloy. The former is often used for castings and is easier to shape, while the latter is usually hot forged and often has better corrosion resistance. These two alloys have further medical applications than the widespread cobalt-chromium alloy and have excellent biocompatibility. They have high tensile strength and good rigidity, and can provide stable mechanical support. On the other hand, these two alloys have high toughness, low notch sensitivity, and excellent fatigue resistance.
The chromium in the alloy can form a dense oxide layer on the alloy surface, which can improve the corrosion resistance of the alloy. The chromium element can also form carbides, which have high hardness and can improve the strength of the matrix and the wear resistance of the alloy. The molybdenum element in the alloy is dissolved in the matrix and can become a barrier to dislocation flow, thereby improving the strength of the matrix.
