Electro-codeposition and properties of Cu–Ni-MWCNTs composite coatings

In this work, multi-walled carbon nanotubes reinforced Cu–Ni matrix (Cu–Ni-MWCNTs) composite coatings were produced using the electro-codeposition method by adding different concentrations of MWCNTs (0.05, 0.1 and 0.15 g L−1) to the Cu–Ni plating bath. To achieve effective dispersion of the MWCNTs, the plating solution was stirred using an ultrasonicator (20 kHz and 500 W) for 120 min. Cu–Ni-MWCNTs composite coatings were characterised by scanning electron microscopy and X-ray diffraction to study the surface morphology and microstructure of the coatings. In addition, the effects of MWCNTs on the microhardness, wear resistance and electrical conductivity of the coating were investigated by microhardness tester, pin on disk wear tester and four-point probe system respectively. All Cu–Ni-MWCNTs composite coatings showed enhanced microhardness and wear performance as compared to the Cu–Ni coating. The Cu–Ni-MWCNT (0.15 g L−1) composite coating exhibited maximum microhardness of 438 HV and minimum wear loss of 0.9 mg among all the coatings, in the same pin-on-disk test conditions, which is attributed to the combined effect of microstructural refinement, higher content of MWCNTs and superior properties of MWCNTs. Electrical studies reveal that MWCNTs play a vital role in increasing electrical conductivity by 1.21 times of magnitude.