An experimental study on corrosion resistance of Ti35 alloy and its high-fluence hydrogen bombardment behavior

Abstract

Ti35 alloy (Ti-6wt.%Ta) shows great potential for nuclear applications due to its excellent performance. However, the effects of corrosion and irradiation on the alloy are not fully understood. This study explores how residual stress and fluoride (0−10.0 mmol L⁻¹) impact electrochemical corrosion and the microstructure changes from high-fluence hydrogen irradiation (1.8–7.2 × 10²⁵ ions·cm⁻²). Findings indicate that the presence of tantalum facilitates the formation of the protective Ta₂O₅ layer and then improves the alloy's corrosion resistance. Cold rolling and annealing enhance Ti35's corrosion resistance by increasing the homogeneity of phase compositions and reducing residual stresses. However, increased fluoride in HNO₃ forms hydrofluoric acid, which dissolves the oxide layer and decreases corrosion resistance, as quantified by increasing the corrosion rate from 0.0446 to 1.5178 mm·a⁻¹. Despite this, the alloy maintains a passivated state with a balance between dissolution and reformulation of the passivation layer. Hydrogen ion implantation at 1000 K leads to the formation of phases such as TiH_0.71, H₂, and TiH₂, and higher implantation fluences reveal more exposed grain boundaries and increased surface dehydrogenation. These insights are crucial for understanding Ti35's stress corrosion behavior and irradiation damage in nuclear facilities.