Performance of Cobalt Chromium Alloy

Update:22 Dec 2017

Cobalt Chrome Alloy is a hard alloy that is resistant t […]

Cobalt Chrome Alloy is a hard alloy that is resistant to all types of wear and corrosion and high temperature oxidation. Commonly known as cobalt chromium tungsten alloy or cobalt-based alloy, Cobalt-Chromium Alloy by the American Elwood Hayness in 1907 invented. Cobalt-Chromium Alloy is based on cobalt as the main component, containing a considerable amount of nickel, chromium, tungsten and a small amount of molybdenum, niobium, tantalum, titanium, lanthanum and other alloying elements, and occasionally also contains a class of iron alloy. Depending on the composition of the alloy, they can be made into wire, powder for hard surfacing, thermal spraying, spray welding and other processes, can also be made into castings and forgings and powder metallurgy.

The size and distribution of carbide particles in the Cobalt-Chromium Alloy and the grain size are sensitive to the casting process and the casting process parameters have to be controlled in order to achieve the required long-term strength and thermal fatigue properties of the Cobalt Chromium Alloy component. Cobalt-Chromium Alloy need to be heat treatment, mainly to control the precipitation of carbides. For Castor too alloy, the first high-temperature solution treatment, the temperature is usually about 1150 ℃, so that all the primary carbides, including some MC-type carbide dissolved in solid solution; and then at 870-980 ℃ aging treatment , The carbide re-precipitation.

Cobalt-Chromium Alloy has good resistance to hot corrosion, is generally believed that Cobalt-Chromium Alloy superior to nickel-based alloys in this reason, the melting point of cobalt sulfide than nickel sulfide melting point, and sulfur in cobalt The diffusion rate is much lower than in nickel. And since most Cobalt-Chromium Alloys contain a higher amount of chromium than nickel-based alloys, alkali metal sulfates are formed on the alloy surface. However, Stellar alloy anti-oxidation capacity is usually much lower than the nickel-based alloy. Early Cobalt-Chromium Alloy with non-vacuum smelting and casting process. Later developed alloy, such as the Mar-M509 alloy, due to containing more active elements zirconium, boron, etc., with vacuum smelting and vacuum casting production.

Cobalt-Chromium Alloy will appear in the topological phase with phase such as Sigma phase and Laves is harmful, will make the alloy brittle. Cobalt-Chromium Alloy less use of intermetallic compounds for strengthening, because Co3 (Ti, Al), Co3Ta and other high temperature is not stable enough, but in recent years the use of intermetallic compounds to strengthen Cobalt-Chromium Alloy has also been developed. Cobalt-Chromium Alloy carbide thermal stability is better. When the temperature rises, the carbide grows faster than the γ-phase in the Ni-based alloy, and then re-dissolves in the matrix at a higher temperature. Therefore, when the temperature rises, the Cobalt Chromium Alloy's strength decreases generally slow.