Electroless NiP micro- and nano-composite coatings (original) (raw)
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Ceramics International, 2014
The formation of a uniform nickel phosphorous (Ni-P) electroless (EL) coating on micron-sized SiC particles was investigated in this study. Metal coated ceramic particles could be used in applications including as the fabrication of cast metal matrix composites.Such ceramic particles have a better wettability in molten metal. In this work, the effects of EL coating parameters, SiC particle size and morphology on the coating uniformity and mechanical bonding at the SiC/Ni-P interface were studied. The results indicated that etching treatment was very effective (especially for coarse powders) on the mechanical bonding at the interface. Theoptimum values of bath temperature and pH were determined to be 50 7 2 1C and 8 7 0.2, respectively. The best uniformity and mechanical bonding were obtained for SiC particles with average particle size of 80 μm (considered relatively as coarse powders in this study). The ball milling of SiC particles (with the average particle size of 80 μm) for 1 h led to the formation of a multi-modal particle size distribution which resulted in a non-uniform quality of particulate coating. The larger SiC particles after ball milling were more completely covered by the Ni-P coating compared to the smaller more fragmented particles. The smaller ceramic particles processed via Ni-P EL coating lead to formation of segregated clusters of Ni-P and therefore such ceramic particles contained many uncoated parts.
Coatings
In this study, electrodeposition of NiP composite coatings with the addition of SiC 100 nm was carried out on low carbon steel studying the effect of additives (sodium dodecyl sulfate, saccharin), particles load (10 or 20 g/L) and current density (1, 2 and 4 A/dm2). As a benchmark, coatings from an additive-free bath were also deposited, despite additives being essential for a good quality of the coatings. The coating’s morphology and composition were evaluated by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). It was shown that by addition of sodium dodecyl sulfate (SDS), pure NiP coating with a higher P content was achieved, and their morphology changed to nodular. SDS also reduced the codeposited fraction of SiC particles, while saccharin increased it. SiC loading and current density had less impact respect to the additives on codeposition of SiC particles. Finally, the microhardness of NiP coatings did not increase linearly by codeposition ...
STRUCTURE AND WEAR RESISTANCE PROPERTIES OF ELECTROLESS Ni-P ALLOY AND Ni-P-SiC COMPOSITE COATINGS
European Chemical Bulletin, 2013
To verify the relationship between the properties of composite coatings prepared on steel and the SiC content of electroless Ni-P-SiC composite coatings. Systematic experiments have been conducted to study the possibility of incorporating solid SiC particles in Ni-P matrix. Kinetics of Ni-P plating reveal that the rate of deposition was found to increase linearly with time. The reduction process of nickel ions by hypophosphite was completely hindered at pH < 2and the minimum temperature at which the bath can be practically operated was about 65 ˚C. The mode of deposition of Ni-P film has been explored in the light of deposition condition. XRD analysis of the as-plated and heat -treated samples revealed the existence of crystalline Ni 3 P phases for the heat -treated alloy. Finally a component electroless Ni-P-SiC composite plating process producing a high wear resistance of the coating. *Corresponding Authors *
Electroless Ni-P composite coatings
Journal of Applied Electrochemistry, 2003
This review outlines the development of electroless NiP composite coatings. It highlights the method of formation, mechanism of particle incorporation, factors influencing particle incorporation, effect of particle incorporation on the structure, hardness, friction, wear and abrasion resistance, corrosion resistance, high temperature oxidation resistance of electroless NiP composite coatings as well as their applications. The improvement in surface properties offered by such composite coatings will have a significant impact on numerous industrial applications and in the future they will secure a more prominent place in the surface engineering of metals and alloys.
Insight of the interface of electroless Ni–P/SiC composite coating on aluminium alloy, LM24
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).
Development of electroless NiP–PTFE–SiC composite coating
Surface and Coatings Technology, 2003
Electroless nickel (EN) and EN composite coatings with polytetrafluoroethylene (PTFE) andyor 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.
Tribological study of Ni matrix composite coatings containing nano and micro SiC particles
Electrochimica Acta, 2005
Nickel matrix composite coatings containing micro and nano-sized SiC particles were prepared from an additive-free Watts' type solution under direct and pulse current conditions, in order to study the correlation between SiC particles embedding and the tribological behaviour of deposits. The wear properties of Ni/SiC composite coatings were shown to depend on the type of current, the size of the embedded particles, the weight fraction of codeposited particles, the microstructural modifications induced by codepositing SiC particles and the plating conditions. It was proved that the presence of SiC particles influences the adsorption-desorption phenomena occurring at the metal-catholyte interface during electrocrystallization and, synergically with the plating conditions, modifies the deposits microstructure thus affecting wear properties.
The electroless nickel composite (ENC) with various silicon carbide contents was deposited onto aluminium alloy (LM24) substrate. The wear behaviour and the microhardness of the composite coating samples were investigated and compared with particles free and aluminium substrate samples using micro-scale abrasion tester and microhardness tester respectively. The wear scar marks and wear volume were analysed by optical microscope. The wear tracks were further studied using scanning electron microscopy (SEM). The embedded particles were found to get pressed into the matrix which helps resisting further wearing process for composite samples. However, random orientation of microcuts and microfallow were seen for ENC sample but more uniform wearing was observed for EN sample. The composite coating with low content of SiC was worn minimum. Early penetration into the substrate was seen for samples with higher SiC content. Microhardness was improved after heat treatment for all the samples containing various SiC content. Under dry sliding condition, inclusion of particles in the matrix did not improve the wearing resistance performance in as-deposited state. The wearing worsened as the content of the particles increased generally. However, on heat treatment, the composite coatings exhibited improved wear resistance and the best result was obtained from the one with low particle contents.