Most cobalt-based alloys contain Chromium. Alloying elements such as Tungsten, Molybdenum, Nickel, Iron, Aluminium and Carbon provide a wide range of properties, e.g. high hardness and resistance to wear and high-temperature corrosion. Fields of application are primarily in the chemical industry, energy technology, aerospace and medical technology.
The basic alloy combination of most alloys is cobalt-chromium, with chromium acting as a strengthening element. Adding tungsten and/or molybdenum can enhance this effect. Another common alloying element is nickel. The material properties are highly dependent on the other alloying elements such as tungsten, iron, aluminium and carbon, as well as the method of manufacture. Co-based alloys are usually produced as remelting grades.
Because of their high melting point and good resistance to high-temperature corrosion, cobalt-based alloys are often used as high-temperature materials. In addition, cobalt-based alloys have high hardness, high resistance to wear and thus good resistance to erosion corrosion. However, these alloys have a somewhat lower creep rupture strength and lower resistance to creep than nickel-based alloys.
Cobalt-based alloys are mainly used in the chemical industry, in energy technology as well as in aerospace and medical technology. Examples of the application of cobalt-based alloys are guide vanes in turbines, abrasion-resistant protective coatings, internals in waste incineration plants or industrial furnaces as well as linings of the combustion chambers of gas turbines and medical implants including dental implants.
Cobalt-based alloys are usually divided into three categories:
– High-carbon alloys, also called Stellites (C from 0.5 to 3%) for highest wear stress, preferably alloyed with Cr (approx. 27 -33%) and W (up to approx.18%) and Mo and therefore a significant proportion of eutectic carbides whose size and distribution strongly depend on the composition, on the solidification conditions. These alloys are mostly used as PM products and in cast form. Only a few of the common alloys can be hot formed.
– Alloys with lower C-content for high temperature applications, mainly with W or Ta, moderate additions of Ni and Cr and occasionally additions of rare earth metals (e.g. lanthanum, yttrium) as well as Al, Ti, Nb for age hardening. These alloys do not have the great technical importance as the Ni-based superalloys, but play a role because of the excellent corrosion resistance, especially against hot gas corrosion even in S-containing environments. These alloys are formable and can be produced in all common product forms, but preferably as sheets and plates.
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– Alloys with low C-content for applications under wet, corrosive conditions and at the same time higher wear stress, primarily alloyed with Cr, Ni and Mo, less with W. The low C content reduces the tendency to precipitate intergranular grain boundary carbides and contributes to the excellent resistance of these alloys to local corrosion effects, e.g. pitting and crevice corrosion and intergranular corrosion. For this reason, such alloys based on Co-Cr-Mo, Co-Cr-W-Ni and Co-Ni-Cr-Mo are preferred for various medical implants and diverse medical metallic structures.
BÖHLER L035 is a 35-cobalt-35-nickel-20-chromium-10-molybdenum wrought alloy (UNS R30035) in the form of bar material. It is a vacuum induction melted (VIM) and vacuum arc remelted (VAR) superalloy. This alloy is typically used in the oil and gas and chemical industries where a combination of high strength, good fatigue resistance, toughness, ductility and exceptionally good corrosion resistance after subsequent ageing is required. However, its use is not limited to such applications. BÖHLER L035 is a nickel-cobalt based multiphase alloy system with a unique combination of properties e.g. extremely high strength, toughness, ductility and excellent corrosion resistance. The alloy can be strengthened and aged in the factory to achieve strength values of over 260 ksi (1793 MPa) and stress corrosion cracking (SCC) resistance even in hydrogen sulphide. The BÖHLER L035 alloy resists pitting and crevice corrosion caused by seawater, chloride solutions and other corrosive environments, e.g. mineral acids (nitric, hydrochloric, sulphuric acid).
Read MoreBÖHLER L035 is a 35-cobalt-35-nickel-20-chromium-10-molybdenum wrought alloy (UNS R30035) used for the production of surgical implants. This alloy composition has been successfully used in human implants. Long-term clinical experience has shown an acceptable biological response. The exceptional properties of BÖHLER L035 result from its chemical composition, high-quality melting technology, cold forming and heat treatment. It is a vacuum induction melted (VIM) and vacuum arc remelted (VAR) superalloy. BÖHLER L035 is a nickel-cobalt based multiphase alloy system with a unique combination of properties e.g. extremely high strength, toughness, ductility and excellent corrosion resistance. The alloy can be strengthened and aged in the factory to achieve strength values of max. 260 to 300 ksi (1793-2086 MPa) and stress corrosion cracking (SCC) resistance even in hydrogen sulphide. The BÖHLER L035 alloy resists pitting and crevice corrosion caused by seawater, chloride solutions and other corrosive environments, e.g. mineral acids (nitric, hydrochloric, sulphuric acid).
Read MoreBÖHLER L135 is a low carbon cobalt-28chromium-6molybdenum alloy (UNS R31537) known as Alloy 1 of this group of metals in the form of bar and wire, typically used for the manufacture of surgical implants, e.g. endoimplants like hip-joints. The alloy composition covered by this specification has been successfully employed in human implants. Long-term clinical experience has shown an acceptable level of biological response. The alloy shows good corrosion resistance and good fatigue and wear resistance. This alloy is especially applicable for medical implants (endoprothesis and osteosynthesis), wherever high mechanical stress is expected. It is also widely used in micromechanics and watchmaking industries, where hardness, toughness, ductility and corrosion resistance are required. It is non-magnetic.
Read MoreBÖHLER L605 is a wrought cobalt-20chromium-15tungsten-10nickel alloy used for surgical implants. The properties specified apply specifically to wrought bar, rod, wire BÖHLER L605 is a nonmagnetic cobalt-based chromium-tungsten nickel alloy that has excellent corrosion and oxidation resistance, and high strength at both room and elevated temperatures. Usually BÖHLER L605 is supplied solution heat treated and quenched condition to attain optimum properties. Through work hardening, high strength levels can be obtained and BÖHLER L605 can be used in the cold worked and aged condition. Applications include medical implant devices, e.g. stents, springs, valves, and engine components for the aerospace industry. The alloy composition covered by this specification has been successfully employed in human implants. Long-term clinical experience has shown an acceptable level of biological response.
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