Laser-Ablated Tungsten as an Interfacial Architecture for Tantalum Coatings: Suppression of Shutdown-Stage Water Corrosion in Accelerator-Driven Neutron-Source Targets

Water-cooled tungsten targets may remain in contact with stagnant deionized water during accelerator shutdown, creating a beam-off corrosion condition distinct from irradiation-assisted service. Untreated tungsten (W), laser-ablated tungsten (LA-W), and a 500 nm tantalum-coated laser-ablated tungsten surface (Ta-LA-W) were therefore immersed in deionized water for up to 28 days. Laser ablation replaced the machined surface with a hierarchical micro/nanostructure and increased the areal roughness Sa from 0.22 ± 0.01 to 1.75 ± 0.07 μm; after Ta deposition, Sa was 1.62 μm. LA-W exhibited the largest topographic attenuation and the highest dissolved W concentration, reaching 7.915 mg·L−1 at 21 days. Ta-LA-W maintained Sa within the range from 1.60 ± 0.06 to 1.66 ± 0.07 μm and limited dissolved W to 1.118–1.601 mg·L−1. X-ray photoelectron spectroscopy showed increased WOx-related intensity and disappearance of the metallic-W loss feature only for untreated W. The W 4f envelopes of LA-W and Ta-LA-W remained broadly similar before and after immersion, but for different reasons: sustained W dissolution for LA-W and suppression of W oxidation and release by the Ta-containing barrier for Ta-LA-W. The dissolution-based corrosion sequence was LA-W > W > Ta-LA-W. Laser texturing therefore acted as an interfacial-engineering treatment rather than an intrinsically corrosion-resistant modification.