Electrochemical dissolution of hard metal alloys

Different components of hard metals such as TiC, TiN, pure Ti and the binder metals Fe, Co and Ni were investigated in neutral sodium nitrate solutions by cyclovoltammograms at current densities up to 35 A/cm2. All combinations of TiN and TiC dissolve anodically. The surface of pure Ti is blocked by the anodic surface oxide which is not removed by cathodic current densities up to 30 A/cm2. Cathodically all samples were conductive and showed a strong hydrogen evolution. The binder metals Fe, Co and Ni should be free of oxide films at cathodic potentials. Anodically, Co dissolves in an active state while Fe and Ni show a potential shift to the passive region. Our surface model developed for machining of Fe seems to be applicable to all other materials except pure Ti.