<p>This study elucidates the laser shock peening (LSP)-induced enhancement of interfacial interdiffusion and the formation of a distinct multilayer structure at the Ti-6Al-4V/Ni coating interface. Following LSP and subsequent vacuum diffusion treatments, a reaction layer comprising five distinct zones with varying thicknesses formed: residual Ni, Ni solid solution, Ni₃Ti, NiTi, and NiTi₂. Beyond the NiTi₂ layer towards the Ti substrate, three characteristic regions were identified: flake distribution, mesh distribution, and substrate. Crucially, LSP significantly enhanced the interdiffusion of elements. The diffusion distance of Ni was greater in β-Ti than in α-Ti, with Ni content in β-Ti exhibiting a characteristic rapid-slow-rapid-slow decreasing trend. Notably, LSP promoted the diffusion of Ni into both α-Ti and β-Ti, and critically, also accelerated the diffusion of Ti towards the Ni side. This enhanced bidirectional diffusion resulted in increased growth rates and thicknesses of the NiTi and NiTi₂ layers. With the increase of laser power, the diffusion coefficient of Ni in β-Ti also increases and the diffusion coefficient is in 10^− 13 m²s^− 1 level. The promotion of interdiffusion by LSP is attributed to the introduction of lattice distortion, elevated dislocation density, grain refinement, and residual compressive stress at the interface. These findings provide significant insights for enhancing the performance of Ti-6Al-4V/Ni coatings in demanding applications and contribute to the design of more durable and efficient material systems for aerospace and automotive industries.</p> Graphical Abstract <p></p>