Effects of 5th element addition to Co-29Cr-6Mo alloy containing impurity ni on metal ion release

In order to investigate the effects of 5th element addition to Co-29Cr-6Mo-1Ni alloys on metal ion release, Co-29Cr-6Mo-1Ni-X(X=Ti, Nb, Al, Zr) alloys were immersed in 1 mass% lactic acid solution at 37°C for 7 days and released metal ions were examined by ICP-AES. All of the 5th element added alloys showed less Ni ion quantities released from various alloys than that released from the original Co-29Cr-6Mo-1Ni alloy. This result suggests that Ni ion release could be suppressed by Ni-fixation mechanism due to the formation of Ni-X compounds (X=Ti, Al, Nb, Zr). Furthermore, the quantities of Co ion from Co-29Cr-6Mo-1Ni-X(X = Ti, Zr) alloys were a half less than that from the original. Each metal ion quantity released from Co-Cr-Mo-Ni alloys consisting hcp phase is lower than that from the alloys consisting fcc phase. From the relationship between microstructure and released metal ion quantity, Co-Cr-Mo-Ni alloys consisting hcp phase exhibit low released metal quantities compared to those consisting fee phase. Therefore, it is likely that metal ion release is suppressed by controlling microstructure through the alloying method.