Preparation and characterization of Ni-coated Cr3C2 powder by room temperature ultrasonic-assisted electroless plating

Ni-coated Cr3C2 powder was prepared by ultrasonic-assisted electroless plating process without conventional sensitization and activation treatments at room temperature. The growth mechanism of Ni layers and the effects of Cr3C2 powder concentration on plating rate and coating quality were studied. Surface morphologies and composition of initial Cr3C2 powder, pre-treatment Cr3C2 powder and Ni-coated Cr3C2 powder were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the Ni layers on the Cr3C2 powder had cell structure with dense and uniform distribution. The growth mechanism of Ni layers appears as follows: the pretreated surfaces of Cr3C2 powder act as activated sites, nucleation and the growth of nickel grains take place on the powder surfaces, and the process repeats continuously on the lath particles with reticulate structure on the as-coated surfaces of previously deposited Ni-cells, finally Ni cells grow up and merge into a layer. With the increase of Cr3C2 powder concentration, the plating time becomes shorter accordingly and the optimal powder concentration is 40 g L−1.