BioDur 108 Alloy is an essentially nickel-free austenitic stainless alloy developed by Carpenter Technology Corporation in response to nickel-allergy problems that have been associated with nickel-containing stainless alloys that have been used in medical applications. The anstenitic structure of this alloy is maintained by a high nitrogen content of approximately one percent. Besides austenitic stability, the high nitrogen content also contributes to high levels of corrosion resistance and strength. The corrosion resistance and strength properties of BioDur 108 alloy are compared to several nickel-containing austenitic stainless alloys that have been used as biomaterials. The strength of such alloys tends to be dominated by nitrogen content, while corrosion resistance is strongly related to the combined contents of chromium, molybdenum and nitrogen. However, the quantitative effect of nitrogen variations on the corrosion resistance observed in high nitrogen alloys is significantly different than in alloys with lower nitrogen levels. In addition, the high manganese content of high nitrogen alloys affects the corrosion characteristics in certain tests, in particular the passive current density measured during potentiodynamic corrosion testing at rapid scan rates. However, it was found that the passive current densities of high nitrogen -high manganese alloys quickly decay to the levels of the comparative alloys in potentiostatic current decay tests and in potentiodynamic tests at slower scan rates.
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