Nanostructuring of Additively Manufactured Stainless-Steel Surfaces for Superior Boiling Heat Transfer

While stainless steel offers unique advantages for thermal applications in corrosive environments, it is resilient to traditional nanostructuring techniques such as chemical etching for heat transfer augmentation. In this work, we fabricate a 304L stainless steel alloy using directed energy deposition additive manufacturing, which leads to a metastable microstructure state that facilitates efficient and scalable etching using chloride species. We unveil a two-step etching mechanism that results in the formation of a network of micro- and nanoscale surface structures. This structured surface shows a 5-fold enhancement of the heat transfer coefficient at significantly lower superheat during pool boiling of water, attributed to increased nucleation in suitably sized cavities created by etching. Our work illustrates the vast potential of advances in additive manufacturing techniques for the development of highly efficient and compact thermal systems.