Electrochemical Surface Modification of Laser Cladded Ni-Based Single Crystal Superalloy in NaNO3 Solution

TL;DR

This paper explores using electrochemical dissolution to achieve smooth surfaces in laser-repaired Ni-based single-crystal superalloys.

Contribution

The study demonstrates electrochemical dissolution as a promising method for shape accuracy in laser-clad superalloys.

Findings

Dendritic and interdendritic regions in the substrate dissolved at different rates, causing a rough surface.

Dendritic and interdendritic regions in the cladding structure dissolved simultaneously, resulting in a smooth surface.

Phase dissolution preferences explain the difference in surface quality between substrate and cladding.

Abstract

Since mechanical processing can introduce stress in the sample, electrochemical dissolution has been utilized to attain shape accuracy in certain materials. However, this technique is rarely applied to laser-repaired Ni-based single-crystal superalloys. In this work, the transpassive dissolution behaviors of an additive manufacturing-repaired Ni-based single crystal superalloy in a 10% NaNO3 solution were investigated by comparison with the substrate. A significant disparity in dissolution rates was found between the dendritic and interdendritic regions of the substrate, resulting in a rough surface. Conversely, the dissolution of the dendritic and interdendritic regions in the cladding structure occurred nearly simultaneously, leading to a high-quality, smooth surface. This behavior was attributed to the differences in phase dissolution preferences between the substrate and the cladding structure. It indicates that electrochemical dissolution is a promising method for achieving shape accuracy in laser-clad Ni-based single-crystal superalloys.

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