Cobalt alloys have been in use since early 1900s in the cobalt–chromium compositions. Historically, many of the commercial cobalt-base alloys are derived from the Co–Cr–W and Co–Cr–Mo ternaries. Cobalt alloys have good magnetic properties, corrosion resistance, wear resistance, and high temperature strength. These properties arise from the crystallographic nature of cobalt, the solid-solution-strengthening effects of Cr, W, and Mo, the formation of metal carbides, and the corrosion resistance imparted by chromium.
Application Note: Determination of cobalt alloys with FOUNDRY-MASTER Smart
Co-Cr has a very high specific strength and is commonly used in gas turbines, dental implants, and orthopedic implants. These alloys show high resistance to corrosion due to the spontaneous formation of a protective passive film composed of mostly Cr2O3, and minor amounts of cobalt and other metal oxides on the surface. As its wide application in biomedical industry indicates, Co-Cr alloys are well known for their biocompatibility.
Stellite is a family of completely non-magnetic and corrosion-resistant cobalt alloys of various compositions that have been optimized for different uses. The alloys may also contain tungsten or molybdenum and a small but important amount of carbon. The alloy currently most suited for cutting tools, because this alloy is quite hard, maintains a good cutting edge at high temperature, and resists hardening and annealing. Other alloys are formulated to maximize combinations of wear resistance, corrosion resistance, or ability to withstand extreme temperatures.
Stellite alloys display outstanding hardness and toughness and are also usually very resistant to corrosion. Typically, a Stellite part is precisely cast so that only minimal machining is necessary. Due to the very high hardness many alloys of Stellite are primarily machined by grinding, as cutting operations in some alloys cause significant tool wear even with carbide inserts. The alloys also tend to have extremely high melting points due to the cobalt and chromium content.
In order to cover all the important alloy elements, the FOUNDRY-MASTER Smart allows the measurement of high Ni, Cr and W alloyed materials and of course special alloys e.g. with Mo, Nb or C. Virtually every Co alloy can be measured accurately on-site with this versatile instrument.
Download the application note for more information.