Achieving wide temperature range of gentle film boiling on textured hydrophobic tool surfaces

Hydrophobic tool surfaces have become a hot topic in recent years due to their significant advantages such as anti-adhesion and friction reduction. However, enhancing hydrophobicity would inadvertently decrease the Leidenfrost point of droplets, which diminishes the heat transfer efficiency and compromises manufacturing quality. This issue presents a considerable challenge and underscores the critical need to understand the boiling dynamics when droplets encounter heated hydrophobic surfaces. Herein, we propose a kind of textured hydrophobic tool surface based on laser processing and hydrophobic coating technology, which could achieve gentle film boiling across a wide temperature range. The raised micropillars protect hydrophobic coating with excellent abrasion resistance and stabilizes the droplets in the gentle film boiling regime under harsh conditions. The primary rationale behind this advancement is the reduction in the critical temperature for film boiling and the elevation of the critical temperature for droplet rebound. We have developed a predictive model for the Leidenfrost point, which has been experimentally validated to determine the wall temperature necessary for achieving the gentle film boiling regime. In addition, we found that the textured hydrophobic surface can still inhibit the bouncing and spreading of droplets at high temperatures. This study not only deepens our understanding of the effects of droplets on heated surfaces but also has the potential to improve manufacturing performance by consistently maintaining the hydrophobic properties of tool surfaces during cutting operations.