Nickel-phosphorous Coatings Research Articles

The effect of phosphorous content on the microstructure and localised corrosion of electroless nickel-coated copper

A detailed microstructural and electrochemical analysis of electroless nickel phosphorous (NiP) coatings with P contents of 13.2 ± 1.2 wt%, 12.9 ± 0.7 wt%, and 8.3 ± 0.8 wt% on a copper substrate was performed to study the corrosion behaviour of electroless NiP/Cu systems. The P content of the electroless NiP coatings plays an essential role in the microstructure of the coatings in terms of crystallinity. The crystallinity variations, representing the extent of crystalline and amorphous phases within the material, with P content, affect the local electrochemical characteristics and, hence, the corrosion protection behaviour of electroless NiP coatings. The coatings with the highest P content showed the best corrosion performance in a 3.5 wt-% NaCl solution. In contrast, the surface of the electroless NiP coatings with low P content is more susceptible to corrosion due to the presence of locations with heterogeneous electronic properties that initiate localised corrosion. Microgalvanic interactions with a high cathode-to-anode surface ratio govern the localised corrosion kinetics of the low P-content samples. A high concentration of nodule boundaries and/or other existing structural defects on the surface serve as anodic sites, whereas the remainder of the surface serves as cathodic sites.

Influence of Deep Cryogenic Treatment on the Properties of Electroless Nickel-Phosphorous Coating

Influence of Deep Cryogenic Treatment on the Properties of Electroless Nickel-Phosphorous Coating

Microstructure, composition and formation mechanism of ultra-black surfaces on the electrodeposited nickel-phosphorous coatings

Light absorbing materials are of practical importance in the production of optical devices in aerospace technology. A new method of light absorbing coatings preparation on the basis of electrodeposited nickel-phosphorus coatings has been proposed. Modification of the electrolyte for nickel-phosphorus plating by the addition of saccharine allowed preparing an ultrablack surface with a reflectance coefficient less than 0.5%. Chemical composition of both surfaces has been studied using X-ray photoelectron spectroscopy. The mechanism of their formation has been proposed. It has been found that etching in nitric acid leads to the partial oxidation of both surfaces with the formation of needle like microstructure.It also results in surface enrichment with phosphorus and formation of nickel phosphides particles of the variable composition. Products of the coating oxidation represent the matrix of amorphous nickel polyphosphates and polyphosphoric acids where fine Ni-P particles are distributed. Such composite structure is a well light absorbing medium. Formation of hypophosphite protective layer on the Ni–P coating obtained from saccharin free electrolyte reduces the thickness of light absorbing layer and changes its composition. Thus light absorbance ability of the coatings can be caused by both distribution of fine nickel-phosphorus particles in dielectric matrix and specific microstructure of their surfaces.

Enhanced mechanical properties and corrosion resistance of nickel and nickel-phosphorous coatings fabricated by electrodeposition embedding with TiB2 ceramic particles

Pure nickel (Ni), TiB2 reinforced nickel (Ni-TiB2), nickel-phosphorus (Ni-P), and TiB2 reinforced nickel-phosphorus (Ni-P-TiB2) composite coatings were deposited on AISI-1045 steel substrates from Watts bath and phosphorous-containing solution, respectively. The composition and microstructure of these coatings were analyzed by energy dispersive x-ray spectroscopy (EDS), scanning electron microscope (SEM) and x-ray diffraction (XRD) analysis. The properties of these coatings, including hardness, were assessed and compared. The electrochemical performance of these coatings was investigated in a 3.5 wt% sodium chloride solution using electrochemical spectroscopy (EIS) and the potentiodynamic polarization technique at room temperature. The effect of TiB2 on the microstructure, phase, and properties of the coatings was investigated. The results indicate that the incorporation of TiB2 particles in the nickel matrix greatly increased the hardness and anti-corrosion properties of the nickel coatings by refining of the microstructure and reducing the defects. The enhancement effect of TiB2 on Ni-P coating is not as significant as that of TiB2 on nickel coating. However, with the incorporation of TiB2 ceramic particles, the corrosion resistance and hardness of the Ni-P-TiB2 coating increased by about 50% and 10%, respectively, compared with the original Ni-P coating. The present study provides insight into the potential applications of novel TiB2 ceramic particle-reinforced nickel composite coatings in the areas of wear and corrosion resistance.

Wear and mechanical properties of electroless NiP and NiP-Silicon Carbide (SiC) composite coatings on En8 steel

Electroless coating technique is widely used in various industrial applications. This coating is the decision for some design applications with different actual attributes of electroless Nickel coatings, for example, hardness, wear resistance and coating thickness. The major advantages of Electroless Ni-P coatings are uniform coating thickness, improved wear and corrosion resistance, hardness, ability to deposit on surface activated non-conductors etc. In this article, a pure Nickel phosphorous (NiP) and Nickel phosphorous-Silicon Carbide (SiC) composite coatings are deposited on En8 steel using electroless coating to enhance the mechanical and wear properties of En8 steel. The wear test was carried out using Pin on Disc Tribometer against the counter part of stainless steel at atmospheric condition with various process parameters such as load, sliding velocity and sliding distance. The surface hardness and elemental composition of the coating were analyzed by Vickers hardness test and Optical Emission Spectroscopy respectively.

Friction and wear behaviour of BN(h) and Ag incorporated nickel phosphorous coatings under dry reciprocating sliding conditions

ABSTRACT Ni–P–BN(h)–Ag hybrid composite coatings were fabricated on the steel substrate by a scalable electroless deposition process. The optimum bath composition and operating conditions were selected to obtain defect-free composite coatings with ∼50 μm thickness. Further, to enhance the hardness, as-deposited coatings were subjected to heat treatment in a tubular furnace at 400°C for 1 h. The dry sliding wear behaviour of the as-deposited (AD) and heat-treated (HT400) composite coatings was evaluated using a linear reciprocating tribometer. The average friction coefficient of the hybrid coating was ∼0.14 (in as-deposited condition) and ∼0.16 (in heat-treated condition); these values represent 51.72% and 52.94% reduction over non-hybrid Ni-P coatings. The specific wear rate of the as-deposited and heattreated composite coatings was found to be 50% and 43% lower, respectively, than that of conventional Ni–P coatings. Detailed wear track analysis was carried out to identify underlying wear mechanisms and tribochemical interactions.

High-temperature Compressive Performance of Mg Alloy Foams Coated with Ni-P Layer

Mg/Ni hybrid foams were fabricated by the electroless method. The Ni-P (Nickel-Phosphorous) coatings were deposited on the surface of closed-cell Mg alloy foams. The composition, microstructure and phases of the Ni-P coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The compressive tests were performed on the Mg/Ni hybrid foams at 400 °C using the Mg alloy foams as a reference. The experimental results show that the yield strength, plateau stress and energy absorption capacity of the closed-cell Mg alloy foams at high temperature were improved by the Ni-P coating. And there are four main modes for the Mg/Ni hybrid foam failure at 400 °C, i e, shearing in cell wall, bending in cell edge, shedding and cracking in Ni-P coating.

Effect of structure of electrodeposited nickel-phosphorous coatings on their physico-mechanical and corrosion-protective properties

Effect of structure of electrodeposited nickel-phosphorous coatings on their physico-mechanical and corrosion-protective properties

Mechanical properties and tribological behaviour of electroless Ni–P–Cu coatings on corrosion-resistant alloys under ultrahigh contact stress with sprayed nanoparticles

Threaded components manufactured from corrosion resistant alloys (CRA's) are vulnerable to galling. This paper develops a test matrix to systematically investigate the mechanical properties and tribological performance of electroless nickel phosphorous coatings on CRA's when subjected to high contact stress. Samples manufactured from 28Cr stainless steel were shot-peened for various periods prior to being electo/electroless coated. The coefficient of friction (CoF) of different coating systems was evaluated via sliding cross-pin method. Various wet and dry lubricants were utilised to examine tribological performance, furthermore the adhesion strength of the coatings was investigated by a bond and pull-off method. The study has shown a significant reduction in CoF for electroless nickel phosphorous coatings with prior shot-peening treatment and sprayed nanoparticles.

Monolayered versus multilayered electroless NiP coatings: Impact of the plating approach on the microstructure, mechanical and corrosion properties of the coatings

Electroless nickel-phosphorous (NiP) coatings were produced on low carbon steel substrates for a total plating time of 3 h. Different preparation modalities were pursued. Multilayered coatings were produced by stacking three layers of the same composition by successive electroless plating with rinsing steps in between. On the other hand, coatings termed ‘monolayered’ for the sake of comparison were deposited by one step electroless process, with and without undergoing bath replenishment of the electrolyte during plating. All the samples were subjected to thermal annealing at 400 °C for 1 h under argon atmosphere.The results show that the multilayer approach prevents crack propagation in the as-deposited coatings because the interfaces between layers block the advance of defects. Bath replenishment during monolayered coatings production creates pseudo-interfaces similar to those of the multilayered case but they are ineffective in terms of corrosion protection. Un-replenishment of the electrolyte promotes a change in the coating's microstructure from lamellar to columnar which severely worsens their performance. Upon annealing, the presence of interfaces, along with the recrystallization of the metallic matrix, promotes an upgrading of the corrosion performance of the multi-layered coatings. The corrosion products spread laterally at the interface where they stockpile. At a certain point, the accumulation of these by-products provokes the exfoliation of the outermost layer exposing the layer underneath to the corrosive media, thereby delaying the advancement of the corrosion attack. The results of this study highlight the importance of the plating approach selection, as well as the need for proper electrolyte maintenance during the production of high-performance electroless coatings.

Fabrication and investigation of the scratch and indentation behaviour of new generation Ni-P-nano-NiTi composite coating for oil and gas pipelines

Oil and gas pipelines operate under severe mechanical and chemical conditions, which could lead to catastrophic failure. Electroless nickel-phosphorous (Ni-P) coatings are an excellent candidate for protection against wear and corrosion for oil and gas pipelines. Ni-P coatings exhibit superior corrosion resistance over many commercially available coatings, as well as high hardness. However, electroless Ni-P coatings suffer from low toughness, which has limited its use in applications where high scratch and dent resistance is required. To enhance the toughness of the Ni-P coatings, nano-sized particles of superelastic NiTi alloy were incorporated within the coating. In the present work novel Ni-P-nano-NiTi composite coating has been successfully plated on API X100 pipe steel. Scratch tests under constant and increasing loads were performed to determine the effect of NiTi nano-particles on wear damages. Indentation tests were carried out to assess the dent resistance and crack modes of the coating. The addition of superelastic nano-particles into the Ni-P matrix led to toughening through transformation toughening, crack bridging, deflection, and microcracking. The composite coatings exhibited lower hardness in comparison to monolithic Ni-P coatings, but still provided considerable improvement upon the steel substrate. Optical and scanning electron examinations showed evidence of delamination, radial, and Hertzian cracking, as well as a reduction in crack length with the addition of superelastic NiTi.

Performance Evaluation of Nano Additives and Surfactants on the properties of Electroless Nickel Phosphorous Coating on Aluminium – Magnesium Alloy

Corrosion occurs as a result of the interaction of a metal with the environment. The extent of corrosion depends on the type of the metal and the surrounding environment. This paper focuses on the investigation of the corrosion problem in Aluminum–Magnesium alloys and experimentally develops an Electroless Nickel - Phosphorouscoating with different nano additives and surfactants. This paper investigates the different types of Electroless Nickel - Phosphorouscoatings done to reduce corrosion in Al-Mg alloys. Two types of nano particles such as nano Al2O3 and nanoZnO with two types of surfactants such as SDS and CTAB were used in this investigation. Different corrosion evaluation tests such as atmospheric exposure test, and wet corrosion test were carried out on the coated samples. Coated samples were characterized with help of Scanning Electron Microscope and Energy Dispersive X-ray Spectrometry. Mechanical evaluation tests such as surface roughness and hardness were measured on the coated samples. Comparison was done between the different EN-P coatings to optimize the concentration ofnano additives and surfactants.

Corrosion behaviour of electroless high boron-mid phosphorous nickel duplex coatings in the as-plated and heat-treated states in NaCl, H2SO4, NaOH and Na2SO4 media

The corrosion behaviour of electroless nickel–boron and nickel-phosphorous coatings, as monolayers and duplex systems was investigated with and without heat-treatment (400 °C - 1 h, non-reactive atmosphere). Monolayer coatings with 20 μm of thickness were compared with duplex coatings composed of two 10 μm layers. Four distinct configurations of duplex coatings were prepared: NiB/NiP; NiP/NiB; NiB/NiB and NiP/NiP. The salt spray test showed that visible differences exist in terms of general corrosion: corrosion starts after 24 h for the NiB samples and after 48 h for the NiP samples. In addition, image analysis was used to quantify the corroded surface after salt spray. The duplex coatings presented intermediate behaviour when compared to the monolayer systems. Furthermore, the corrosion behaviour was evaluated by means of potentiodynamic polarisation technique. Results clearly suggested that monolayer NiP exhibits higher corrosion resistance than monolayer NiB. In all cases, polarisation tests showed that a NiP layer is preferable as the outer part of the coating rather than a NiB layer. Finally, cross-section analysis allowed better understanding of the corrosion properties.

The Structure and Main Characteristics of Diamond-Bearing Ni–P Coatings

The effect of detonation-synthesis nanodiamonds (extracted from detonation products by thermal treatment in air in the presence of boric anhydride) on the characteristics of chemical composite nickel–phosphorous coatings has been investigated. It has been established that the introduction of nanodiamonds results in formation of a finer structure of the obtained coatings, reduction in the size of the coherent-scattering region, and an increase in the size of the crystal-lattice parameter. The coatings’ microhardness increased by 30% on average. Application of nanodiamonds with a surface modified with nickel compounds has yielded an additional increment of the microhardness of composite coatings by 33%.

Electrochemically promoted electroless nickel-phosphorous plating on titanium substrate

An electrochemically promoted electroless nickel–phosphorous plating process on titanium substrate is proposed. The influences of the temperature and current density on the phosphorous content, coating thickness and corrosion resistance are investigated. The results show that with the help of the electrochemical promotion, the uniform and amorphous nickel–phosphorous coatings with medium phosphorus content (6–8wt%) are successfully prepared in the electroless bath at 40–60°C. The phosphorous content of the coating increases with the temperature increasing, while decreases with current density increasing. Obvious passivation occurs for the nickel–phosphorous coatings during the anodic polarization in 3.5wt% NaCl solution.

Adhesivity of electroless Ni-P layer on austenitic stainless steel

Purpose: Optimization of testing of adhesivity of electroless deposited nickel-phosphorous coatings on austenitic stainless steel substrate. Design/methodology/approach: The main study has been focused on comparison of testing methods of adhesivity of electroless nickel- phosphorous coatings and analyses of influence of heat treatment on adhesivity of electroless nickel- phosphorous. Findings: It was found out that adhesivity of electroless nickel- phosphorous coatings can be successfully characterized by Vickers hardness tester. Research limitations/implications: The study was not extended to other types of deposited layers in order to be able to bring a general decision about applicability of this method in the testing of adhesivity of deposited layers. Practical implications: Based on experimental results it was found out that heat treated nickel-phosphorous coating have higher microhardness than non-heat treated electroless nickel-phosphorous coatings. High microhardness of heat treated nickel-phosphorous coating is connected with formation of Ni3P phase. Moreover, better adhesivity can be achieved by application of proper activation process before electroless coating. Originality/value: Standard Vickers hardness method was successfully applied in testing of adhesivity of electroless nickel- phosphorous coatings on austenitic stainless steel substrate.

Electroless Deposition of Composite Nickel-Phosphorous Coatings with Diamond Dispersoid

AbstractThe composite Ni-P coating with diamond particles (D) deposited on the flexible substrates of pressed polyethylene terephthalate material (PET) was obtained, to be used in the development of efficient, flexible grinding and polishing tools. The optimal conditions of the hydrodynamic regime, deposition time and temperature were found. The influence of the concentration and size of the D particles (3/7 ÷ 225/300 μm) on the coating thickness and number of co-deposited particles were studied. By Scanning Electron Microscopy (SEM) images were defined the morphology of dispersion coatings and number of co-deposited particles in them, and Energy Dispersive Spectroscopy (EDS/INCA) was used to determine the elemental chemical composition of the composite coatings.

Nanoindentation and nanoscratch behavior of electroless deposited nickel-phosphorous coating

Electroless nickel-phosphorous (NiP) coating was deposited on steel substrate followed by annealing at 600 °C in an argon atmosphere. Nanoindentations and nanoscratch experiments were performed on the as-deposited and annealed coating. Improvement of 32% in hardness was found on annealing the coating, which might be due to the two major phenomena. Firstly, presence of Ni3P precipitates which accelerated the bowing of dislocations and observed to be the dominant mechanism in increased hardness. Secondly, diffusion of iron (Fe) and chromium (Cr) atoms from the substrate to the coating. Scherrer technique and TEM analysis showed the increase in Ni grain size on annealing. Annealed coating showed an enhancement of 31% in elastic modulus compared to as-deposited coating. Increased elastic modulus could be due to the reduction in triple junction and grain boundary as a result of increased grain size. Strain hardening exponent was found higher for annealed coating (0.33) compared to as-deposited coating (0.25) indicating lower pile-up formation in annealed coating during indentation. Higher scratch hardness resulted lower scratch width and depth for the annealed coating. Coefficient of friction decreased from 0.30 for as-deposited coating to 0.23 for annealed coating, resulting 58% reduction in calculated wear rate of the scratch of annealed coating. Direct correlation was observed between nanoindentation and nanoscratch results of as-deposited and annealed NiP coatings.

Surface Characterizations of Fretting Fatigue Damage in Aluminum Alloy 7075-T6 Clamped Joints: The Beneficial Role of Ni-P Coatings.

This paper aims to characterize the surface damage as a consequence of fretting fatigue in aluminum alloy 7075-T6 plates in double-lap bolted joints through XRD, surface profilometry, and SEM analyses. The main focus was on the surface roughness and chemical phase composition of the damaged zone along with the identification of fretting fatigue crack initiations over the surface of the material. The surface roughness of the fretted zone was found to increase when the joint was clamped with a higher tightening torque and tested under the same cyclic loading. Additionally, MgZn2 (η/ή) precipitates and ZnO phase were found to form onto the surface of uncoated aluminum plate in the fretted and worn zones. The formation of the ZnO phase was understood to be a result of frictional heat induced between the surface of contacting uncoated Al 7075-T6 plates during cyclic loading and exposure to the air. The beneficial role of electroless nickel-phosphorous (Ni–P) coatings in minimizing the fretting damage and thus improving the fretting fatigue life of the aluminum plates was also studied. The results showed that the surface roughness decreased by approximately 40% after applying Ni–P coatings to the Al 7075-T6 plates.

Studying the Effect of the Concentration of PTFE Nanoparticles on the Tribological Behavior of Ni-P-PTFE Composite Coatings

In the past 30 years, electroless nickel (EN) plating has grown to such proportions that these coatings and their applications are now found underground, in outer space, and in a myriad of areas in between. Moreover, in order to further improve the mechanical and tribological properties of the nickel-phosphorous (Ni-P) coatings, Ni-P/PTFE composite coatings can be obtained, which provides even greater friction behavior and lubricity than the one naturally occurring in the nickel-phosphorous alloy deposit. In this paper, The Ni-P-PTFE coating was deposited on mild carbon steel surface via electroless deposition process. The friction behavior and wear mechanisms of Ni-P-PTFE nanocomposite coating were studied at different concentrations of PTFE. Frictional behavior was examined using a pin on disk wear test method. Surface morphology and worn surface was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) analysis. The results showed that the incorporation of PTFE nanoparticles can reduce the wear rate of Ni-P coating from 33.07×10-6 mm3/Nm to 12.46×10-6 mm3/Nm for the Ni-P PTFE containing 10 g/l PTFE and decrease the friction coefficient from 0.64 to 0.2. Thus the tribological behavior of Ni-P coating is much improved in the presence of PTFE nanoparticles and 10 g/l is the optimized concentration of PTFE in the electroless bath.