Reoxidation process and corrosion behavior of TA15 alloy by laser ablation

Abstract

The thermal oxide layer formed of TA15 alloy has poor corrosion resistance. In this paper, the changes of the elements and components on the surface after laser ablation with different energy densities (E) were researched. The formation process and corrosion behavior of laser-generated oxide layer were clarified. As E increases, the oxygen content decreases from 8.52% to 5.43% and then increases to 11.89%. The surface oxide layer changes from TiO2(R) (i.e., rutile) to Ti2O3 + TiO2(R) and finally becomes TiO2(R) + TiO2(A) (i.e., anatase). The TiO2(R) gasification was confirmed by calculating the surface temperature rise. The surface reoxidation process was illustrated by a thermodynamically calculated ∆G-T(i.e., the Gibbs free energy changes with temperature). When E ≥ 17.5 J·cm−2, the oxide layer exhibits an agitated morphology, and oxide falls off at the bottom. As E increases, the corrosion rate decreases first and then increases. With energy density of 8.75 J·cm−2, the surface corrosion rate was 20.43 times slower than that of the untreated sample. The impedance spectrum and equivalent resistance results also prove the best corrosion resistance at 8.75 J·cm−2. The corrosion behavior of the oxide layer is analyzed from the properties of the oxide layer components and the reaction products with the electrolyte.