Coordinated regulation of corrosion and wear properties of Zr alloy by constructing surface gradient microstructure using fiber laser

Although R60702 Zr alloy is a strong passivation material, it is susceptible to pitting corrosion in Cl⁻ environments and exhibits poor wear resistance, which limits its range of applications. This work synergistically manipulates the surface corrosion and wear resistances of R60702 Zr alloy through surface phase control and gradient microstructural design. A gradient structure composed of fine αʹ martensitic slats is achieved by laser surface remelting and quenching, leading to the formation of passive film with excellent corrosion resistance. Meanwhile, a uniformly varying surface gradient structure is constructed at a laser power of 500 W, along with finer and more uniformly distributed ZrFe₂ precipitates. Additionally, the oxide film thickness is increased, rendering superior corrosion resistance in Cl⁻ environments. The increase in grain and subgrain boundary area and high-density dislocations owing to martensitic phase transformation enhance the surface hardness and improves the wear resistance. Particularly, the gradient variations in grain size and phase structures lead to the gradient increase of pitting resistance and hardness from the substrate to surface, which is anticipated to enhance the endurance of the surface modification layer. Our convenient way of constructing surface gradient microstructure provides a valuable reference for elevating the surface corrosion and wear resistances of Zr alloys.