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.