Microstructure and behavior of laser-mixed Cr/Ni films on Cu alloys

Abstract

Deposited thin films of Cr and Ni on Cu substrates have been melted and intermixed with a frequency-doubled Q-switched Nd:YAG laser. The laser pulses melt the thin films and a shallow portion of the substrate. Resolidification interface volocities are on the order of 1–10 m s⁻¹. Rutherford backscattering, Auger spectroscopy, and energy dispersive x-ray mapping have been used to characterize the elemental distribution. Channeling and transmission electron microscopy were used to investigate the microstructure of the surfaces produced. In contrast to the binary Cr–Cu system, where extended solid solutions are produced, the Cr–Ni–Cu system results in a metallic glass surface. We have found that these metallic glass surfaces, which have been dubbed “stainless coppers,” exhibit excellent hydrogen sulfide corrosion resistance. Their contact resistance is low and stable over long periods of time and through tens of thousands of electronic dial switching cycles.