Crystallisation and Phase Transformation Behaviour of Electroless Nickel-Phosphorus Deposits and Their Engineering Properties

Abstract

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.

Microstructure and corrosive property of Ni-P/nano-CeO2 coating electrolessly prepared in acidic condition

“…Ni-P coating may have different structures changing from poly-crystal, micro-crystal, nano-crystal to amorphous state due to its different phosphorous contents under different depositing conditions, and usually acidic condition may promote the final amorphous state and high P content [2][3][4][5][6] . In the experiment, the electroless bath is the same for two coatings except nano-CeO 2 addition, while P contents in CeO 2 -free and CeO 2 -containing coatings have different values of 10.5 wt% and 12.6 wt%, respectively.…”

“…Its chemical and mechanical property depends much on its microstructure and phosphorous content. Furthermore, the internal phase transformation of electroless Ni-P coating in high temperature environment has been widely studied by researchers [3][4][5][6] . It is commonly recognized that phosphorous content in Ni-P coating will determine the coating's structure in the range of normal ploy-crystalline, micro-crystalline, nano-crystalline and amorphous structure.…”

“…It is commonly recognized that phosphorous content in Ni-P coating will determine the coating's structure in the range of normal ploy-crystalline, micro-crystalline, nano-crystalline and amorphous structure. Usually, the mechanical property of Ni-P coating can be improved through the addition of secondary hard or lubricant phase into the coating, such as the addition of superfine SiC, Si 3 N 4 , Al 2 O 3 and PTFE (polytetrafluoroethylene) particles [2][3][4] . The actual depositing mechanism of Ni-P coating has not been fully understood yet, and few research on rare earth element addition has been reported.…”

Recent advances in electroless-plated Ni-P and its composites for erosion and corrosion applications: a review

“…1 [24]. The hardness is reduced beyond 400°C due to the formation of lattice defects and with the coarsening of Ni 3 P particles [25]. Zhao et al investigated the effects of low temperature annealing on the properties of amorphous Ni-P alloys over different periods [26].…”

Strategy to Improve the High-Temperature Mechanical Properties of Cr-Alloy Coatings

“…Additionally, the hardness level attained after annealing at these temperatures (~13.0 GPa) is substantially above that reported for other metal-metalloid deposits such as electroless and electroplated Ni-P coatings, which generally exhibit maximum hardness values of at most~8.8 GPa at substantially lower annealing temperatures (T < 500°C). [16][17][18][19][20][21][22] This strength enhancement after annealing suggests that ternary Cr-C-P coatings may find use in applications Fig. 4.-Effect of annealing temperature and phosphorus content on hardness of electrodeposited Cr-C-P coatings.…”