Effect of vapor deposition in shrouded plasma spraying on morphology and wettability of the metallic Ni20Cr coating surface

A Ni20Cr coating surface with a micro-nano hierarchical structure was successfully prepared by shrouded plasma spraying method in the present study. By adjusting the spraying parameters to control the heating degree of the powder particles and using a designed shield deposition method, we confirmed that the nanostructures were the products of vapor deposition by vaporization of the material during the spraying. In addition, an interesting phenomenon was found that, without any additional chemical modification, the surface with micro-nano structures underwent a wettability transition from superhydrophilicity to super-hydrophobicity during the storage in air. The results show that the selective spontaneous adsorption of the nanostructures can effectively reduce the surface free energy. The nanostructures deposited on the top of the surface made the surface form a unique hierarchical structure, which can effectively reduce the contact area of the droplet with the surface. Nanostructures affected the wettability of the coating surface both in the chemical composition and the structural aspects, which demonstrated that they were the key to obtaining super-hydrophobic property on the coating surface. (C) 2017 Elsevier B.V. All rights reserved.