3D hot laser shock peening without coating based on Leidenfrost effect enables self-armored hydrophobic surface with enhanced fatigue properties

Abstract

Hydrophobic metal surfaces have widespread applications in self-cleaning, ice removal, corrosion resistance, and drag reduction. The fine structure of these surfaces is crucial for their hydrophobic properties. Currently, pulse laser direct surface texturing is commonly employed to create hydrophobic surfaces, but this method primarily operates at room temperature. However, the rapid cooling rate and significant temperature gradient of the thin melted layer generated at room temperature often result in high stress concentration and cracks within the fine structure, compromising the overall integrity of the hydrophobic surface when subjected to complex external loads. To assess structural robustness by evaluating crack propagation, fatigue performance serves as a vital indicator. The thermal effect helps mitigate thermal cracking caused by direct laser irradiation and introduces an additional strengthening mechanism through dynamic strain aging. By utilizing the Leidenfrost effect, water can act as a confinement layer to achieve high temperature laser shock, which is expected to enhance the fatigue performance of hydrophobic structures. In this study, we propose a technique called 3D hot laser shock peening without coating (3HLSPwoC) as a cost-effective and efficient method to fabricate multi-scale self-armored hydrophobic surfaces with enhanced fatigue properties. We systematically discuss and analyze the wettability and mechanical properties of samples manufactured using different approaches. Furthermore, we reveal the underlying mechanism responsible for the fatigue performance improvement achieved through the 3HLSPwoC process, supported by molecular dynamics calculations and finite element simulations. Compared with the samples manufactured at room temperature, the surface of 3HLSPwoC samples exhibit greater plastic deformation, with no visible cracks on the surface. Additionally, these samples possess higher compressive residual stress and hardness. Notably, 3HLSPwoC samples demonstrate superior fatigue performance and enhanced durability of the hydrophobic properties. 3HLSPwoC has proved to be a novel process for manufacturing advanced hydrophobic surfaces with comprehensive mechanical properties.