Structure and phase transformation behaviour of electroless Ni–W–P on aluminium alloy

In this paper, the structure and phase transformation behavior of as-deposited and heated Ni–W–P deposits on aluminium alloy were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Deposits were heated at temperatures ranging from 200 to 600 for 1 h. The TEM images of the as-deposited and heated at 200 for 1 h deposits resolve the nanocrystalline grain structure. The thermal stability of electroless Ni–W–P deposits, analyzed by DSC, could be enhanced by the co-deposition of tungsten as compared to binary electroless Ni–P coating. The composition of Ni–W–P and Ni–P were determined by EDS. The phase of Ni–W–P was evaluated by XRD technique and a small mount of tungsten could cause Ni lattice expansion. The co-deposition of tungsten could enhance the atomic blinding force against regional plastic deformation. Surface hardness of binary alloy deposit could also be modified with the introduction of the tungsten element.