Soft Sparking Discharge Mechanism of Micro-Arc Oxidation Occurring on Titanium Alloys in Different Electrolytes

Soft sparking during micro-arc oxidation can form a ceramic coating with high hardness and bond strength on titanium alloy while avoiding the continuous strong that damage substrate properties integrity of coating. Existing studies have reported soft spark discharge is significantly influenced by electrolyte anions, detailed mechanism its influence remains unclear. Therefore, we considered four monolithic electrolytes, namely Na2B4O7, NaF, Na3PO4, Na2SiO3, for bipolar pulsed (MAO) treatment Ti6Al4V to investigate affections different electrolytes discharge. The results showed discharges were observed in both Na2SiO3 Na3PO4 not Na2B4O7 NaF electrolytes. We attributed this situation fact deposition Si P elements changed structure passivation ability affected rate ion transport electron tunneling coating, resulting forming thick dense, MAO inner layer. Additionally, facilitated particle did destroy initial film layer, also had no significant effect corrosion resistance.