Anode plasma electrolytic carburizing of commercial pure titanium

The study investigates the influence of electrolyte compositions with acetone, glycerol, sucrose, ethylene glycol and ammonium chloride on the properties and structure of commercial pure titanium (CP-Ti) in the process of anode plasma electrolytic carburizing (PEC). The wear of the samples was measured using pin-disk friction in lubricated testing conditions. The effects of electrolyte composition on corrosion resistance of the PEC samples were examined by means of potentiodynamic polarization in a solution of sodium sulfate. It is shown that anode PEC of CP-Ti samples leads to formation of solid solution of carbon in titanium and external oxide layer in all studied electrolytes. The mechanism of carbon transfer from electrolytes containing sucrose, ethylene glycol and acetone to treated CP-Ti is found. The anode PEC of CP-Ti samples at 850 °C during 5 min was established to result in decrease in their surface roughness Ra from 1.13 ± 0.01 μm to 0.04 ± 0.01 μm and friction coefficient from 0.29 ± 0.01 to 0.10 ± 0.01. The treatment in the aqueous solution of ammonium chloride (10 wt.%) and sucrose (10 wt.%) resulted in the decrease in the wear rate by 3-3 orders. The base-sucrose electrolyte conditioned a decrease in the corrosion current density by a factor 18 due to passivating effect of the oxide layer.