Structural and phase transformation behaviour of electroless Ni-P and Ni-W-P deposits

Differential scanning calorimetry (DSC) coupled with X-ray diffraction (XRD) and transmission electron microscopy (TEM) is used to elucidate the structural and phase transformation behaviour of electroless Ni-P and Ni-W-P alloys. Synthesis of the coatings was done using acidic electroless bath. The coatings were annealed at 300 and 600 °C for 1 h. X-ray diffraction pattern of all the coatings indicate presence of either amorphous or both amorphous and crystalline phases coexisting. The lattice disorder in the crystalline phases decreased with increasing tungsten content in the deposit. The grain size in the as-deposited crystalline deposit was found to vary from 5 to 40 nm. Annealing the coatings at 300 °C did not produce any appreciable change in grain size. But, annealing at 600 °C increased the grain size to 500 nm.