Nickel-phosphorous Coatings Research Articles

Taguchi -Grey Based Optimization of Friction and Wear of Electroless Ni-P Coatings in Acidic Environment

The present study describes the synthesis of electroless Ni-P (nickel-phosphorous) coatings on mild steel substrate and optimization of the coating process parameters for minimum friction and wear in acidic (1M H2SO4) solution using Taguchi based grey relation analysis. The study is carried out using different combinations of four coating process parameters, namely, concentration of nickel source, concentration of reducing agent, deposition temperature and annealing temperature with three levels each. The tribological tests are conducted with a pin-on-disk tribometer. Analysis of variance reveals that annealing temperature has the maximum contribution in controlling the friction and wear characteristics of Ni-P coating. The coating is characterized using scanning electron microscopy, energy dispersive X-ray and XRD analysis, respectively. It is found that Ni-P coating is amorphous in as-deposited condition but gradually turns crystalline with heat treatment. Moreover the wear mechanism is found to be abrasive in nature.

Effect of reducing agent and nano Al2O3 particles on the properties of electroless Ni–P coating

Abstract This work is an experimental study on the formation, characteristics and properties of electroless nickel phosphorous (Ni–P) coatings and electroless nickel alumina (Ni–P–Al 2 O 3 ) coating with varying reducing agent concentration. The results obtained indicate that the deposition rate and surface roughness of both Ni–P coating and Ni–P–Al 2 O 3 coatings are highly influenced by reducing agent (sodium hypophosphite). With increase in sodium hypophosphite Ni forms amorphous phase and as a result the micro hardness of the coating gets reduced. Heat treatment was carried out at 400 °C for 1 h after the coating, resulted in the formation of an intermetallic nickel phosphide (Ni 3 P) phase which improved the hardness of the Ni–P coating from 400 ± 25 to 700 ± 25 HV. A composite coating is formed due to the incorporation of nano alumina in the Ni–P coating leading to an increase in the hardness. The chemical composition of nickel gets reduced from 85.3 to 77.8 wt.% due to the presence of alumina which resists the deposition of Ni. The uniform distribution of alumina particles are observed using a scanning electron micrograph and confirmed by X-ray diffraction techniques. The specific wear rate of Ni–P–Al 2 O 3 coated and post coating heat treated specimens was observed to be less when compared with that obtained in the case of conventional Ni–P coating.

Design, fabrication, and characterization of electroless Ni–P alloy films for micro heating devices

In this work electroless nickel–phosphorous coatings were used as the micro heaters for scanning thermal microscopy. The deposition of Ni–P alloys not only simplified the microelectromechanical system fabrication steps but also provided flexibility in the tuning of the resistance of the heating elements.Ni–P films were plated on patterned silicon substrates and silicon with a silicon nitride film. The pre-deposition reactive ion etch (RIE) treatment caused a change in surface roughness that enhanced the adhesion of Ni–P coatings. Optimization of RIE parameters and pH values could achieve selective deposition of Ni–P, thus helped the lift-off of a serpentine circuit pattern.The chemical composition and microstructure of Ni–P films affect the electrical properties of micro heaters. Energy-dispersive X-ray spectroscopy identified the Ni–P composition and confirmed its insignificant level of oxidation. The high-temperature X-ray diffraction indicated that the as-deposited film was crystalline Ni, which later transformed into Ni3P at higher temperature. The resistivity of Ni–P films was tailored between 10−5 and 10−7Ωm via a post-deposition annealing, which also obtained a stable temperature coefficient of resistance. Consequently, the performance of micro heaters could be designed with a high degree of flexibility.

Effect of Nanoadditives with Surfactant on the Surface Characteristics of Electroless Nickel Coating on Magnesium-Based Composites Reinforced with MWCNT

An experimental investigation has been carried out on optimizing process parameters of electroless nickel-phosphorous coatings on magnesium composite reinforced with carbon nanotube. A comprehensive experimental study of electroless Ni–P coatings on magnesium composite reinforced with multiwalled carbon nanotube under specific coating conditions was performed. The electroless coating bath consists of nickel sulphate (26 g/L), sodium hypo-phosphite (30 g/L) as reducing agent, sodium acetate (16 g/L) as stabilizer, and ammonium hydrogen difluoride (8 g/L) as the complexing agent. The surfactant SLS was added in the solution for better wetting and spreading of coating on substrate. The stabilizer thiourea (1 ppm) was added in the bath to prevent decomposition of bath. Different nanoadditives such as ZnO, Al2O3, SiO with various concentrations were used in the bath and their influence on coating process characteristics were studied The nano additives such as ZnO, Al2O3, SiO were added at concentrations of 0.1%, 0.5%, 1%, and 2% in the EN bath. The output parameters such as surface roughness, microhardness, specific wear rate, and surface morphology were measured. Surface morphology was studied using scanning electron microscope. The results showed that the proposed method resulted in significant improvement on the quality of the coatings produced.

The Deposition Process and the Properties of Direct Electroless Nickel-Phosphorous Coating with Chromium-Free Phosphate Pickling Pretreatment on AZ31 Magnesium Alloy

The Deposition Process and the Properties of Direct Electroless Nickel-Phosphorous Coating with Chromium-Free Phosphate Pickling Pretreatment on AZ31 Magnesium Alloy

Improving fretting fatigue behaviour of Al 7075-T6 bolted plates using electroless Ni–P coatings

In this paper, the effect of electroless nickel–phosphorous coatings on the fatigue and fretting fatigue behaviour of Al 7075-T6 bolted plates has been investigated. A double-lap bolted joint specimen was designed and manufactured from the aluminium plates and subsequently coated with Ni–P coatings of 40μm in thickness with a high phosphorous content of 10–13wt.%. Then, different tightening torques were applied to clamp the plates together with the aim of studying the effect of clamping force on the fretting fatigue life of the joints. Ni–P coatings were found to protect Al 7075-T6 clamped plates against fretting fatigue damages even at low fatigue loads where the uncoated joints showed a large reduction in their fatigue life due to the fretting effects. Fretting fatigue life of moderately and firmly clamped plates was successfully improved by approximately 30–40% and 50–60% respectively after the application of Ni–P coatings. Furthermore, fatigue cracks were found at the outer surface of the aluminium substrate at the edge of the hole associated with nodular defects whose deleterious effect was more pronounced at high cyclic loads. The Ni–P deposit presented a very good adhesion to the substrate at low and moderate loads; however, considerable delaminations and fracture of the coating film at high cyclic loads was observed.

Prediction of phosphorus content of electroless nickel–phosphorous coatings using artificial neural network modeling

A multilayer feedforward neural network with two hidden layers was designed and developed for prediction of the phosphorus content of electroless Ni–P coatings. The input parameters of the network were the pH, metal turnover, and loading of an electroless bath. The output parameter was the phosphorus content of the electroless Ni–P coatings. The temperature and molar rate of the bath were constant ( $$ 91^\circ {\text{C}},\:0.4\,{\text{Ni}}^{{{\text{ + + }}}} /{\text{H}}_{2} {\text{PO}}_{2}^{{ - - }} $$ ). The network was trained and tested using the data gathered from our own experiments. The goal of the study was to estimate the accuracy of this type of neural network in prediction of the phosphorus content. The study result shows that this type of network has high accuracy even when the number of hidden neurons is very low. Some comparison between the network’s predictions and own experimental data are given.

Corrosion-resistant and protective properties of amorphous nickel-phosphorous coatings

Corrosion-resistant and protective properties of amorphous nickel-phosphorous coatings

CORROSION BEHAVIOUR OF Ni PTFE and Ni Al2O3 COATING

The Objective Of The Present Work Is To Study The Corrosion Behaviour Of Ni Al O Coating Comparing With Other Types Of 23 Coatings Such As Ni PTFE, Nickel Coatings, Nickel Phosphorous Coatings, Chromium Coatings, Nickel Cobalt Coatings And The Bare Metal. The Different Thickness Of Coatings Was Obtained By Adjusting Current Density And Deposition Time. The First Corrosion Test Conducted Is Salt Spray Corrosion Test. The Weight Loss Was Calculated. Among The Electro Deposition Process, The Ni Al2O3 Coatings Have Shown The Highest Hot Corrosion Resistance Followed By Ni-PTFE, Cr, Ni-Co, Ni-P, Ni Coatings And The Bare Metal. Then The Optimum Thickness For Ni Al2O3 Was Obtained.

XRD, XPS and SIMS investigations on electrodeposited nickel-phosphorous alloy coatings

Structural and chemical investigations on electrodeposited nickel-phosphorous alloy coatings by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) are described. Electrodeposition of nickel-phosphorous coatings has been carried out galvanostatically in a hypophosphite bath at two different current densities, namely 20 and 80 mA cm −2. XRD has shown a broad peak indicating an amorphous structure in both cases. XPS shows the presence of Ni 2P compound. XPS also reveals the amount of phosphorous in both coatings to be around 10.20 wt.%. SIMS has shown that the coating deposited at lower current densdity (20 mA cm −2) has a broad coating-substrate interface, possibly due to some porosity in this coating. The presence of some oxygen contamination at the coating-substrate interface is also evidenced through SIMS in both cases. The usefulness of XPS and SIMS in the characterization of electrodeposited coatings is demonstrated.