Nanostructural features in nanoporous copper coatings fabricated by laser deposition

Nanoporous metals are now attracting more and more attention for their novel physical, chemical and mechanical properties. It is of great scientific and engineering significance to deposit nano-structure on macro-component surface to locally achieve nano-properties for potential applications. Laser deposition offers a promising approach to deposit a designed structure with designed composition on any location of a component. Nanoporous copper coatings with nano scale porosities were fabricated in this work by laser deposition and dealloying of copper alloy layer on macro-component surface. The fabrication process is constituted of three steps: 1) laser deposition of a MnxCu1-x powder mixture on steel substrates to obtain layers with exact composition; 2) high speed laser remelting of alloy layers to obtain microstructure refinement and composition homogeneity; 3) electrochemical dealloying of remelted layers to obtain nanoporous structure. Dealloying potential and alloy coatings’ composition take important part in microstructure evolution of nanoporous copper, with great impacts on both size and morphology of the nanoporous structure. Microstructural investigations confirm that there is a critical dealloying potential for nanoporous structure formation. When the potential set to a low level, dissolution of Mn as well as pores evolution is restrained. When the potential set to a high level above the critical, dissolution of Mn gets accelerated resulting in pore coarsening. Moreover, alloy coatings with different chemical compositions result in nanoporous coatings with different microstructures, when dealloyed on their own critical potentials.