Microstructure analysis of a Cr-Ni multilayer pulse-electroplated in a bath containing trivalent chromium and divalent nickel ions

A Cr-Ni multilayer comprised of alternating nanosized amorphous Cr- and crystalline Ni-rich sublayers was successfully prepared by pulse-current electroplating in a plating bath containing Cr3 + and Ni2 + ions. The microstructure of the Cr-Ni multilayer was analyzed with transmission electron microscopy, and the chemical composition was analyzed with Auger electron spectroscopy and a local electrode atom probe (LEAP). The analytical results of the LEAP showed small amounts of Cl, O and N in the Cr-rich layers but not in the Ni-rich ones. This indicates that the reduction of Cr3 + ions is complicated in the vicinity of the cathodic surface. Moreover, Cr tends to form chlorides and oxides during electrocrystallization. The electrocrystallization behavior of the Cr-Ni multilayer is discussed based on the results of the microstructure and chemical composition analyses.