Crystallisation and phase transformation behaviour of electroless nickel-phosphorus deposits and their engineering properties

The crystallisation and phase transformation behaviour of electroless Ni-P deposits during thermal processing have a vital role in determining their material properties. Conflicting results have been reported for the correlation of crystallisation and phase transformation behaviour with deposit composition and thermal processing, and hence microstructure and material properties. These variations are believed to be caused by variations in factors including plating conditions, substrate composition and surface preparation, and testing and measuring techniques. The mechanism of electroless Ni-P plating is discussed briefly and the literature on the effect of crystallisation and phase transformation behaviour on the microstructure and material properties of electroless Ni-P deposits is critically reviewed A comparison is made with other commonly used engineering deposits such as electroplated nickel and hard chromium. The advantages, limitations, and development of electroless Ni-P are outlined and the use of heat treatment to tailor properties for specific industrial applications are described. Finally, the challenges this technology faces in the future are considered.