Evaluation of reinforced Ni–W–Mo ternary alloy coatings on copper substrates

In this study, the structure and mechanical and corrosion properties of Ni–W–Mo alloys in a brine solution were investigated. For this purpose, Ni–W–Mo ternary coating layers were electroplated onto Cu substrates under a pulsed current with different densities (i = 2–12 A/dm2). According to the EDS results, the W content in the ternary alloy coatings increased from 12 to 28 wt. % with increasing current density, whereas the Mo content decreased from 21 to 11 wt. %. The corrosion behavior of the Ni–W–Mo ternary coatings in a brine solution (3.5 wt. % NaCl with 0.1M H2SO4) was investigated by recording dynamic polarization curves. The Icorr values of the Cu substrate and electroplated Ni–W–Mo coating (i = 12 A/dm2) were 7.5 × 10−5 and 2.5 × 10−6 A/cm2, respectively. Furthermore, nanoindentation and slow strain rate tests were performed to examine the mechanical properties of the prepared specimens. The ultimate tensile strengths of the Cu substrates with and without a Ni–W–Mo coating (i = 12 A/dm2) were 266 and 245 MPa, respectively. The higher tensile strength of the Ni–W–Mo coating was ascribed to the precipitation of the amorphous structure, and partially brittle behavior was observed for the Ni–W–Mo coating fracture surface after the slow strain rate test. The incorporation of Mo and W elements into the Ni-based coating significantly improved the corrosion and tensile resistances of the Cu substrate in the brine solution.