Hydrothermal growth of Ni-based coatings on copper substrates

Ni-based coatings were deposited on copper substrates by a hydrothermal approach. The results showed that a Ni-based cellular microstructure was bridged by “fiber-like” products. A high microhardness of Hv 856 was achieved after 400°C heat treatment, which is nine times that of copper substrates (Hv 95). Nucleation, growth, and fusion of Ni atoms along the linear direction, induced by a linear-type citrate-metal structural “molecule template”, led to in-situ growth of Ni-based fibers between cellular microspheres. After 400°C heat treatment, the precipitation of NiP and Ni₃P hard phases contributed to the high microhardness of Ni-based coatings.