Fretting corrosion behaviors and wear–corrosion synergistic interaction of bare and micro-arc-oxidized Ti6Al4V ELI in different fretting regimes

Micro-arc oxidation (MAO) offers an effective and promising route to enhance the tribocorrosion performance of Ti6Al4V. However, the fretting corrosion behavior of MAO-Ti6Al4V and the synergistic interactions between wear and corrosion remain insufficiently understood. To address this gap, Ti6Al4V underwent MAO treatment, and a systematic comparative analysis was conducted on bare Ti6Al4V and MAO-Ti6Al4V under distinct fretting regimes. Fretting damage mechanisms were elucidated, and load- and displacement-dependent fretting corrosion maps, comprising material-loss maps, dominant-mechanism maps, and synergy maps, were constructed to assess fretting loss level, dominant mechanisms, and synergistic responses between wear and corrosion. Results showed that, across a range of loads and displacements, MAO markedly reduced the friction coefficient, fretting loss volume, and corrosion current of Ti6Al4V, thereby improving its fretting state and fretting corrosion resistance. Following MAO, the damage mechanism in the partial slip regime (PSR) shifted from micro-cutting to slight scratching. In MFR, the mechanism in the stick zone evolved from adhesive wear to particle entrapment, while that in the slip zone shifted from abrasive/oxidative wear to abrasive wear. In the slip regime (SR), it transitioned from fatigue wear, abrasive wear, and oxidative wear to abrasive wear. MAO also reduced the corrosion contribution, shifting the dominant mechanism from microabrasion-corrosion dominated to microabrasion dominated. Furthermore, due to periodic passive-film breakdown, synergy for bare Ti6Al4V primarily manifested as mutual promotion between wear and corrosion. By contrast, benefiting from a dense debris layer, synergy for MAO-Ti6Al4V in the SR manifested as mutual inhibition between wear and corrosion.