Electroless Nickel Composite Coatings Research Articles

High Temperature Tribological Behavior of Electroless Plating Ni-P-Si3N4-WS2 Composite Coatings

Electroless nickel composite coatings have the potential for high-temperature tribological applications, and a combination of high wear resistance and low friction factor is one of the desirable solutions but still a tricky problem. The addition of self-lubricating WS2 and hard Si3N4 nanoparticles to the Ni-P coatings is expected to obtain good high-temperature tribological performance. In this work, Ni-P-Si3N4-WS2 composite coatings with various contents of WS2 nanoparticles were prepared using electroless plating and subsequently annealed at 400 °C in an inert atmosphere. The tribological properties of the coatings were evaluated using a ball-on-disc wear instrument at operating temperatures from 25 to 600 °C. The microstructure, chemical composition, and surface morphology of the coatings were characterized by X-ray diffractometry (XRD), energy disperse spectroscopy (EDS), and scanning electron microscopy (SEM). Upon increasing the WS2 dosage in the bath, the WS2 content in the coating increased and the micro-hardness of the as-plated coating increased from 539 to 717 HV. After heat treatment, the coating underwent a crystallization process, and the hardness increased from 878 to 1094 HV. The main wear mechanism of the coating changed from adhesive wear in the as-plated state to abrasive wear in the annealed state. The annealed Ni-P-Si3N4-WS2 coating with a WS2 dosage of 2.5 g/L in the bath exhibited excellent mechanical properties, with a hardness of 10.9 GPa, a friction coefficient of ~0.51, and a wear rate of 8.4 × 10−15 m3N−1⋅m−1 at room temperature, and maintained optimal performance at high temperatures. At operating temperatures of 200, 400, and 600 °C, the form of wear was adhesive wear for coatings with a WS2 dosage <1.5 g/L and abrasive wear for coatings with a WS2 dosage ≥1.5 g/L. The synergism of WS2 and Si3N4 particles refined the grains of the Ni-P matrix in as-plated coatings and obviously reduced the friction coefficient of friction pairs in annealed coatings at all operating temperatures.

Tribology of Electroless Nickel and Interlayer Coatings: A Review

This review emphasizes on the development of electroless nickel composite coatings by incorporating different types of material and interlayers to improve the mechanical and tribological properties of the coatings. Electroless nickel coatings are the main focus of this review as it possesses excellent mechanical and tribological properties such as, hardness, wear and corrosion resistance. Besides, electroless nickel coating may behave as lubricating as well as wear resistance coating compared to other interlayer coatings. Tribology aspect is concern on the friction and wear phenomena which involved the moving parts that measures the overall systems’ life, efficiency, and reliability. Interlayer coatings are applied to improve the adhesion between the substrate and the outer coating materials. Various materials are used as interlayers either pure or compound metallic elements.

Reusing oxide-based pulverised fly ash and medical waste particles to develop electroless nickel composite coatings (Ni-P/fly ash and Ni-P/SiO2-Al2O3)

Recycling and reusing materials from waste have become a nexus in the development of sustainable materials, leading to more balanced technologies. In this study, we developed a composite coating by co-depositing recycled ceramic particles, pulverised fly ash (PFA) and medical ceramics (MC), into a nickel-phosphorus matrix using a typical electroless plating process. Scanning electron microscopy (SEM) images indicated well-dispersed particles in the Ni-P matrix. However, compared with the MC particles, the PFA particles were distributed scantily with a lower content in the matrix, which could be due to the less impingement effect during the co-deposition. A modified microstructure with refined grains was obtained for the PFA-incorporated composite coating, as seen in the SEM micrograph. The X-ray diffraction result of the MC-incorporated composite coating showed the formation of NixSiy phases in addition to the typical Ni3P phases for the heat-treated electroless Ni-P coatings. Upon heat treatment, the PFA-reinforced composite coating, due to a modified microstructure, exhibited a higher microhardness up to HK0.05 818, which is comparable to that of the traditional SiC particle-embedded composite coating (HK0.05 825). The findings can potentially open up a new strategy to further advance the green approach for industrial surface engineering.

Study of nickel matrix composite coatings deposited from electroless plating bath loaded with TiB2, ZrB2 and TiC particles for improved wear and corrosion resistance

The effect of thermally and electrically conductive TiB2, ZrB2 and TiC particles on the stability of high phosphorus electroless nickel (EN) plating bath was studied through particle surface modifications. The EN composite coatings with optimal contents of the hard particles were deposited on carbon steel substrates, characterized in microscopic morphology and composition (optical microscope, SEM/EDS), crystallinity (XRD), and micro-hardness. The composite coatings were evaluated with erosion and corrosion tests. The results showed that the electrically conductive hard particles affect the stability of EN plating bath in the order of TiB2 > TiC > ZrB2, with the utmost impact from TiB2 and insignificance from ZrB2. The incorporation of TiB2 particles trigged a rapid decomposition of an EN plating bath within 2 h, which is likely due to the high catalytic activity of TiB2 particles. The nickel phosphorus (NiP) matrix composite coatings are able to offer a combination of wear and corrosion resistance to effectively protect carbon steel components from corrosion according to the test results, which supports an expectation that the coatings can be used in harsh environments, e.g., those encountered in marine and oil and gas (O&G). The effect of heat treatment on the coating properties, in particular, corrosion and wear resistance were studied and the mechanisms behind the property changes were discussed as well.

Electroless Nickel-Phosphorus Composite Coatings

Electroless nickel composite coatings possess excellent mechanical and tribological properties such as, hardness, wear and corrosion resistance. Composite coatings can easily be coated not only on electrically conductive materials but also on non-conductive materials like as fabrics, plastics, rubber, etc. This review emphasizes on the development of electroless nickel composite coatings by incorporating different types of hard/soft particles (micro/nano size) in the electroless Ni-P matrix to improve the mechanical and tribological properties of the coatings. The preparation of electroless bath for nickel-phosphorus composite coating, methods to incorporate hard and/or soft particles in the bath, factors affecting the particle incorporation in the coating and its effect on coating structure, hardness, wear resistance, friction behavior, corrosion resistance, and mechanical properties are discussed thoroughly.

Insight of the interface of electroless Ni–P/SiC composite coating on aluminium alloy, LM24

Abstract Electroless nickel composite coatings with silicon carbide, SiC, as reinforcing particles deposited with Ni–P onto aluminium alloy, LM24, having zincating as under layer were subjected to heat treatment using air furnace. The changes at the interface were investigated using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) to probe the chemistry changes upon heat treatment. Microhardness tester with various loads using both Knoop and Vickers indenters was used to study the load effect clubbed with the influence of second phase particles on the coating at the vicinity of the interface. It was observed that zinc was absent at the interface after elevated temperature heat treatment at 400–500 °C. Precipitation of copper and nickel with a distinct demarcation (copper rich belt) along the coating interface was seen with irregular thickness of the order of 1 μm. Migration of copper from the bulk aluminium alloy could have been the factor. Brittleness of the coating was confirmed on heat treatment when indented with Vickers. However, in composite coating the propagation of the microcrack was stopped by the embedded particles but the microcracks continue in the matrix when not interrupted by second phase particles (SiC).

Effect of Process Parameters on Corrosion Resistance of Ni-P-Al2O3 Composite Coatings Using Electrochemical Impedance Spectroscopy

Electroless nickel composite coatings are developed by incorporating soft/hard particles into Ni-P coatings, to improve mechanical as well as tribological properties. The objective of the present work is to investigate the effect of various coating process parameters on the corrosion behavior of Ni–P–Al 2O3 composite coating deposited on mild steel substrate. The electrochemical impedance spectroscopy test is used to evaluate the corrosion behavior of the heat treated composite coatings at various annealing temperatures (300 °C, 400 °C, and 500 °C). Corrosion properties, charge transfer resistance ( Rct ) and double layer capacitance ( Cdl ), are optimized using Taguchi based grey relational analysis to improve the corrosion resistance of the coating. Concentration of nickel source, concentration of reducing agent, concentration of alumina particles and annealing temperature, are considered as a main design factor for optimization of electrochemical properties. Analysis of variance (ANOVA) is used to find out the optimum combination of coating process parameters. From ANOVA result, it is found that the concentration of Al 2O3 particles and annealing temperature have significant influence on the corrosion resistance of the composite coatings. Concentration of reducing agent has moderate influence on the corrosion resistance. Surface morphology of the coated surface is studied using SEM (scanning electron microscopy) and chemical composition of the coating is studied using EDX (energy dispersive X-ray analysis). The XRD (X–ray diffraction analysis) is used to understand the phase transformation behavior of the composite coatings.

AN EVALUATION OF NI-P AND NI-P/NANO-SIO2 COATINGS ON SWEET CORROSION OF API-5L-X70 PIPELINES STEELS

Carbon and low alloy steels are the most commonly used construction materials for oil and gas pipelines. In order to improve their performance, various types of coatings are frequently applied on them. Electroless nickel composite coatings containing nano-particles are widely used on steel substrates. In this paper, CO 2 corrosion of X70 carbon steel coated with Ni - P and Ni - P -nano SiO 2 in 3%Wt NaC1 electrolyte, saturated with CO 2 at 85°C and pH 6.5 in 1bar CO 2 pressure for 72 h, was investigated and the results were compared against each other. SEM and XRD techniques were used for investigating the corrosion products morphology and composition, respectively. In addition, the corrosion process was studied using EIS technique. The experimental results showed that the formation of FeCO 3 protective film on coated samples was limited. Moreover, the addition of SiO 2 nano-particles to Ni - P coating improved corrosion resistance of the substrate, which also showed the ability of nano-particle addition to the Ni - P coating in decreasing the corrosion rate.

Wear and corrosion properties of electroless nickel composite coatings with PTFE and/or MoS2 particles

This study focuses on the effect of co-deposition of PTFE and/or MoS2 particles on the morphology, wear, and corrosion properties of electroless nickel coating. The composite coating of EN–PTFE–MoS2 was heat treated at different temperatures for hardness investigations. The surface morphology of coatings was characterized by scanning electron microscopy. Pin-on-disk and potentiodynamic polarization tests were used to study the tribological and corrosion properties of the coatings, respectively. Results of hardness analysis revealed that the hardness of electroless nickel coatings was increased by the heat treatment, and its maximum was gained at 400°C. Wear investigations showed that simultaneous co-deposition of the PTFE and MoS2 particles into the nickel coating increased the wear resistance of the coating by about 30% and reduced the average value of friction coefficient to 0.25 from 0.65. Corrosion studies illustrated that simultaneous co-deposition of the PTFE and MoS2 particles led to reduction in corrosion resistance by 10 and 5 times that of EN coating in brine and acidic solution, respectively.

Influence of cubic nanostructure additions on the properties of electroless coatings

In this research, the influence of co-deposited within nickel-phosphorus matrix cubic nano- and micro-sized particles (nanodiamond and micron cubic boron nitride) on the properties of the composite coatings was investigated. Nanometer diamond was synthesised by using the detonation method. It is a kind of materials with properties of diamond and nanometer particle. High phosphorus electroless nickel bath was used to prepare electroless nickel composite coatings from a suspension. In order to characterise the deposits, their structure, morphology and hardness were analysed. The incorporation of particles has a marginal influence on the composition. The influence of thermal processing of the samples on the coating properties was investigated. The highest microhardness, the superior corrosion and wear resistance of the nickel-phosphorus-nanodiamond composite coating was obtained by heat-treated samples.

An investigation on corrosion resistance of as-applied and heat treated Ni–P/nanoSiC coatings

EN–SiC coatings are recognized for their hardness and wear resistance. In this work electroless Ni–P coatings containing nano SiC particles were co-deposited on St37 tool steel substrate. Scanning electron microscopy (SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD), polarization and electrochemical impedance spectroscopy (EIS) were used to analyze morphology, structure and corrosion resistance of the coatings. The results showed that SiC nano-particles co-deposited homogeneously, and the structure of Ni–P–SiC nano-composite coatings as deposited was amorphous. Heat-treatment at 400 °C for 1 h induced crystallization of the electroless Ni–P coatings. Microhardness of electroless Ni–P–SiC composite coatings increased due to the existence of nano-particles, and reached to a maximum value after heat-treatment. Corrosion tests showed that both electroless nickel and electroless nickel composite coatings demonstrated significant improvement of corrosion resistance in salty atmosphere. Proper post heat-treatment significantly improved the coating density and structure, giving rise to enhanced corrosion resistance.

THE CORROSION BEHAVIOR OF ELECTROLESS Ni-P-SiC NANO-COMPOSITE COATING

Composite coatings constitute a new class of materials which are mostly used for mechanical and tribological applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. In this study, electroless Ni – P composite coatings are formed on St 37 steel through the addition of nano-scale SiC particles to the plating bath. This work aimed to investigate the corrosion characteristics of electroless nickel composite coatings using electrochemical measurements which include polarization and electrochemical impedance spectroscopy tests. The morphology and structure of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The results showed that both electroless nickel and electroless nickel composite coatings demonstrated significant improvement of corrosion resistance in salty atmosphere.

Preparation and characterization of silicon nitride codeposited electroless nickel composite coatings

Ferrous based bearings can be suitably used for water lubricated applications by reducing the corrosion with the application of electroless nickel coating. Enhancement of wear resistance can be achieved by codepositing silicon nitride (Si 3N 4) which possesses high hardness and chemical inertness. This paper reports the characteristic of a typical medium phosphorous (6.5 wt.%) electroless nickel coating. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies showed the amorphous to crystalline transition with precipitation of Ni 3P and Ni around 340 °C even when 2.9 wt.% Si 3N 4 was present in the composite. Results showed increasing co-deposition of second phase upon increasing temperature, pH and bath loading; highest incorporation (4 wt.%) was at 10 g/l of suspension. Scanning electron microscopic (SEM) photographs of the cross-section and surface of coated specimen revealed most desired uniformity at 2.9 wt.% from 5 g/l bath loading. Electrochemical measurements showed that the electroless nickel composite coating with 2.9 wt.% Si 3N 4 (ENC) has almost similar corrosion rate as that of carbon steel in demineralised water adjusted to pH 10 by addition of LiOH. Tribological tests of AISI 52100 ball-bearings and races coated with 4 μm thick ENC in demineralised water of pH 10 using four-ball tester showed satisfactory performances in terms of weight loss, pitting levels and coefficient of friction and life time of about 9 years under the actual application environment.

Heat treatment effects on EN-PTFE-SiC composite coatings

Electroless nickel (EN) composite coatings embedded with SiC and PTFE particles were deposited on mild steel substrates. Postdeposition heat treatment effects on coating properties were studied in a N 2 atmosphere. Differential scanning calorimetry (DSC), X-ray diffractometry (XRD), scanning electron microscopy (SEM), EDX and EIS were used to analyse the temperature dependence of the microstructure, composition, mechanical and corrosion properties of the coatings. It was found that the as-deposited EN-PTFE-SiC coatings had a homogeneous structure with microsized SiC and PTFE particles embedded in an amorphous Ni–P matrix. Phase transition from an amorphous Ni–P matrix to a mixture of polycrystalline Ni and Ni 3P alloy occurred at around 340 °C. The highest microhardness and best adhesion properties were observed for the samples annealed at 400–450 °C for 1 h. It is interesting to note that the embedded PTFE particles were still stable even when heat treated at 450 °C, probably owing to the Ni–P metal matrix package effect. EIS results showed that proper heat treatments also enhanced the corrosion resistance in both acidic (1.0 N H 2SO 4) and salty (3% NaCl) media, attributing to the coating density and structure improvement.

Corrosion resistance properties of electroless nickel composite coatings

Electroless nickel (EN) composite coatings incorporated with PTFE and/or SiC particles demonstrated significantly improved mechanical and tribological properties as well as low surface energy which are desired for anti-sticking and wear resistant applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. This work aimed to investigate the corrosion characteristics of EN composite coatings using electrochemical measurements which include open circuit potential (OCP), electrochemical impedance spectroscopy and potentiodynamic test. The effects of the co-deposited particles on corrosion behavior of the coatings in 1.0 N H 2SO 4 and 3% NaCl media were investigated. The surface autocatalytic properties and the post-heat-treatment on coating corrosion resistance were also discussed. The results showed that both EN and EN composite coatings demonstrated significant improvement of corrosion resistance in both acidic and salty atmosphere. Ni striking substantially enhanced the corrosion resistance due to the improvement of the surface autocatalytic properties and homogeneity. Proper post-heat-treatment significantly improves the coating density and structure, giving rise to enhanced corrosion resistance.

Corrosion resistance properties of electroless nickel composite coatings

Electroless nickel (EN) composite coatings incorporated with PTFE and/or SiC particles demonstrated significantly improved mechanical and tribological properties as well as low surface energy which are desired for anti-sticking and wear resistant applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. This work aimed to investigate the corrosion characteristics of EN composite coatings using electrochemical measurements which include open circuit potential (OCP), electrochemical impedance spectroscopy and potentiodynamic test. The effects of the co-deposited particles on corrosion behavior of the coatings in 1.0 N H2SO4 and 3% NaCl media were investigated. The surface autocatalytic properties and the post-heat-treatment on coating corrosion resistance were also discussed. The results showed that both EN and EN composite coatings demonstrated significant improvement of corrosion resistance in both acidic and salty atmosphere. Ni striking substantially enhanced the corrosion resistance due to the improvement of the surface autocatalytic properties and homogeneity. Proper post-heat-treatment significantly improves the coating density and structure, giving rise to enhanced corrosion resistance.

Development of electroless NiP–PTFE–SiC composite coating

Electroless nickel (EN) and EN composite coatings with polytetrafluoroethylene (PTFE) and/or SiC were deposited by chemical deposition. The microstructure analysis was conducted with scanning electron microscopy and X-ray diffraction. Differential scanning calorimetry was used to study the phase transition of the coating during the heat treatment. The mechanical and tribological properties were measured using hardness indentation, scratch test and pin-on-disc wear test. The surface energy was analysed using water droplet surface contact angle measurement. The synergistic effects of SiC and PTFE on the wear and anti-sticking properties of the coatings are discussed.

Study on Corrosion Resistance of Electroless Nickel Composite Coatings

Study on Corrosion Resistance of Electroless Nickel Composite Coatings

Hydrogen evolution, incorporation and removal in electroless nickel composite coatings on aluminium

The mechanism of electroless nickel deposition involves generation of hydrogen which can be entrapped in the NiP layer. In this study hydrogen evolution in several electroless composite coatings, that is, NiP–X (X=SiC, Al2O3 and boron particles), deposited on an aluminium (6063-T6) substrate, was investigated by the solid extraction method. It was found that particle codeposition can promote hydrogen occlusion in the layers, a fact correlated with the adsorption capacity and affinity of particles towards water or hydrogen itself. Hydrogen removal efficiency from coatings, after heat treatment, increased with the applied temperature (130, 160 and 190 °C for 1.5h each). For the same heat treatment (190 °C for 1.5h), most composite coatings showed lower removal efficiencies (35–54%) compared to NiP layer (80%) and, as the amount of hydrogen in the composite coating increased, its removal efficiency decreased.

Two-body abrasive wear of electroless nickel composite coatings

The two-body abrasive wear of electroless nickel (EN), EN-silicon carbide, and EN-alumina composite coatings have been investigated using a scratch test with a diamond indenter. The coatings were heat treated at temperatures of 100–500° C. The hardness of the coatings increased with heat treatment temperature from 500 HV100 for the as-deposited condition to 1008 HV100 when fully hardened. Scratch testing showed that the as-deposited coating had scratch tracks with a high degree of plasticity, signs of microploughing and tensile cracking and was characterised as a ductile failure. On the other hand, the heat-treated coatings showed chipping and cracking on the edge of the scratch tracks, failing in a brittle manner. The heat-treated EN-silicon carbide coatings, however, exhibited no cracking nor chipping, believed to be due to its higher fracture toughness than the other heat-treated coatings, attributable to its lower phosphorus content. The volume of material removed from the silicon carbide scratch track was 1/3 of the volume removed from the steel substrate at a 20 N load, and showed the best wear/ scratch resistance of any of the coatings tested.