Simultaneous laser nitriding and biomimetic texturing: A synergistic strategy for enhancing mechanical properties and corrosion resistance of Ti6Al4V alloy

Abstract

The service reliability and lifespan of Ti6Al4V in high-end equipment application are limited by its poor wear resistance and susceptibility to pitting corrosion. Pulsed laser nitriding and simultaneous microtexturing can improve surface hardness and wear resistance. However, this method faces a mutual constraint between modified layer thickness and structural regularity. In this study, composite microtextures comprising periodic ripples and uniform vein-like structures are fabricated on Ti6Al4V by CW laser nitriding. Inspired by biological surfaces, various biomimetic textures are created, among which the biomimetic fish scale surface (BFS) exhibits remarkable performance enhancement. Its cross-section consists of a dendritic TiN layer on the surface and a dense acicular α'-Ti phase within the molten pool, with the modified layer thickness increasing to nearly 20 μm. Compared with the substrate, the cross-sectional hardness increases by 117 %, while the wear rate decreases by 10 % and 96 % under dry friction and starved lubrication, respectively. Moreover, the corrosion potential shifts positively from −579.84 mV to −299.47 mV, and the corrosion current density decreases by three orders of magnitude. The formation mechanisms of the microtextures are elucidated based on the evolution of microscopic morphologies and finite element simulations. The hardness enhancement is interpreted through analysis of the cross-sectional microstructure, whereas the improvement in corrosion resistance is revealed through impedance spectroscopy and passive film composition. This work provides a new strategy for the integrated construction of nitrided layers and functional microtextures on titanium alloy surfaces.