Microstructural modification, characterization and corrosion resistance of a biomedical low carbon CoCrMo-alloy
This work focuses on producing different microstructures of a selected CoCrMo (0.07 wt.-% carbon) alloy by melting, solution annealing, plastic deformation, recrystallization and inter-critical annealing. The different generated microstructures were characterized using optical microscopy, SEM including EBSD, EDS, XRD and hardness measurements. Finally, the corrosion behavior of three different microstructures representing typical conditions in hip surgery (cast, recrystallized and deformed) was investigated in a selection of simulated body fluids by electrochemical methods. The influence of adding HCl and H2O2 to the simulated body fluid, which imitates the acidification in crevice conditions and inflammatory cell reactions, was studied. Heat treatment and deformation results in different phase fraction of the hcp phase and higher hardness, while the corrosion behavior remains almost unaffected. The addition of HCl and H2O2 to the simulated body fluid leads to more positive open circuit potentials and higher corrosion current densities and influences the corrosion behavior significantly.