Improvement of electrochemical deposition performance and design of Fe–Ni multilayer structure by nanosecond laser

Abstract

Multilayer (ML) coatings obtained by adjusting the alternating changes in electrical parameters are typically accompanied by a high internal tensile stress. In this study, Fe–Ni ML coatings were electrodeposited by frequent changes in duty cycles between 55 (50 mA/cm2) and 30% (25 mA/cm2). The surface quality, internal structure, mechanical, and corrosion resistance of the electrodeposited ML coatings were evaluated with and without laser irradiation. After the laser was introduced, the surface quality of the ML coating improved, accompanied by fewer surface defects and smaller grain sizes. The Fe content of the electrochemical deposited coating alternated between 40 (25 mA/cm2) and 54 wt% (50 mA/cm2), and that of the coating prepared by laser-assisted electrochemical deposition alternated between 18 (25 mA/cm2) and 42 wt% (50 mA/cm2). This difference is due to the laser thermal and force effects on the abnormal Fe–Ni co-deposited coating. In addition, the residual internal stress changed from tensile to compressive, and the surface microhardness improved. The friction coefficient decreased from 0.34 to 0.27, indicating better wear resistance. In addition, the electrochemical test results show that the ML coating prepared by LECD has better corrosion resistance. Finally, the strengthening mechanism of the laser in the preparation of the Fe–Ni ML coating is summarized. Combined with the abnormal co-deposition reduction characteristics of Fe–Ni, an ML structure with controllable elemental contents (horizontal and vertical) and better quality can be obtained by adjusting the laser parameters without changing the electrochemical parameters.