  Radio-frequency (RF) contacts-which are an example of electrical contacts-are
commonly employed on accelerators and nuclear fusion experimental devices. RF
contacts with a current load of 2 kA for steady-state operation were designed
for application to the International Thermonuclear Experimental Reactor (ITER)
device. In contrast to the typical working conditions of general commercial
electrical contacts, those of RF contacts employed on fusion devices include
high vacuum, high temperature, and neutron radiation. CuCrZr is currently of
interest as a base material for the manufacture of louvers of RF contacts,
which has excellent thermal and electrical properties and has low creep rate at
250 {\textdegree}C. In this study, a hard Au coating (Au-Ni) was electroplated
on CuCrZr samples and the samples were then subjected to thermal aging
treatment at 250 {\textdegree}C for 500 h in order to simulate the
vacuum-commissioning process of the ITER. The effects of thermal aging on the
hardness, elastic modulus, crystallite size, and compositions of the coating
were investigated via microstructural and mechanical characterizations of the
coating material. Metal atom migration in different coating layers during
thermal aging was characterized and evaluated via scanning electron
microscopy/energy dispersive X-ray spectroscopy observations of the
cross-sectional surfaces, and the obtained results could be used to directly
select the coating thickness for the final RF contact component. The contact
resistance-an important parameter of the RF contact-was measured in a dedicated
testbed built to simulate fusion reactor conditions between CuCrZr pins and
stainless steel plates coated with Au-Ni and Rh, respectively.
