https://pureadmin.qub.ac.uk/ws/files/126683921/Edited_sudagar_R1.pdf

Electroless nickel, alloy, composite and nano coatings – A critical review

Wear behavior of Ni–P and Ni–P–Al2O3 electroless coatings

Corrosion resistance enhancement of electroless Ni–P coating by incorporation of ultrasonically dispersed diamond nanoparticles

Corrosion resistance enhancement of Ni–P electroless coatings by incorporation of nano-SiO2 particles

Superfine silicon carbide particles reinforced nickel-phosphorus(Ni-P)matrix composite coatings were prepared by electroless depositionThe morphology and structure as well as the phase transformation of the composite coatings were studied by SEM,XRD,TEM and DSCIt is shown that SiC particles co-deposited homogeneously,and the structure of Ni-P-SiC composite coatings as deposited was amorphousAfter certain heat treatment,the matrix of composite coatings crystallized into nickel crystal and nickel phosphideAt higher temperature,nickel reacted with SiC and generated nickel silicides accompanied by free carbonFinal products of Ni- P-SiC coating after completely heat treatment were consisted of Ni,Ni_3P,Ni_3Si and carbonThe finer the SiC particles in composite coating,the lower the temperature for the reaction to take place

Electroless Ni-P-SiC Composite Coatings with Superfine Particles

High phosphorus electroless nickel bath has been used to prepare composite coatings containing alumina powders (50 nm, 0.3 μm and 1.0 μm). Deposits were characterized for its structure, morphology and hardness. Incorporation of particle has a marginal influence on the composition. More amount of particle incorporation and uniform distribution was found in composite coatings obtained with 1.0-μm (C3) alumina particles compared to 50-nm (C1) and 0.3-μm (C2) alumina particles. XRD results showed a broad peak of nickel and low intensity alumina peaks present in C3 composite coating in as-plated condition. A marginal improvement in hardness was noticed in as-plated composite coatings. A 15% increase in microhardness was observed in the heat-treated (400 °C for 1 h) composite coatings. Potentiodynamic polarization measurements made on these deposits in 3.5% sodium chloride solution showed that uniform corrosion occurred in C1 and C2 composite coatings whereas localized corrosion was observed in C3 composite coating.

Influence of particle size on the microstructure, hardness and corrosion resistance of electroless Ni–P–Al2O3 composite coatings

Surface morphology and structure of electroless ternary NiWP deposits with various W and P contents

In the present investigation electroless ternary NiWP–Al2O3 composite coatings were prepared using an electroless nickel bath. Second phase alumina particles (1 µm) were used to codeposit in the NiWP matrix. Nanocrystalline ternary NiWP alloys and composite coatings were obtained using an alkaline citrate based bath which was operated at pH 9 and temperature at 88 ± 2 °C. Mild steel was used as a substrate material and deposition was carried out for about 4 h to get a coating thickness of 25 ± 3 µm. Metallographic cross-sections were prepared to find out the coating thickness and also the uniform distribution of the aluminum oxide particles in NiWP matrix. Surface analysis carried out on both the coatings using scanning electron microscope (SEM) showed that particle incorporation in ternary NiWP matrix has increased the nodularity of composite coatings compared to fine nodular NiWP deposits. Elemental analysis of energy dispersive X-ray (EDX) results showed that codeposited P and W elements in plain NiWP deposit were 13 and 1.2 wt.%, respectively. There was a decrease in P content from 13 to 10 wt.% with a marginal variation in the incorporated W (1.01 wt.%) due to the codeposition of aluminum oxide particles in NiWP matrix. X-ray diffraction (XRD) studies carried out on as-plated deposits showed that both the deposits are X-ray amorphous with a grain size of around 3 nm. Phase transformation studies carried out on both the coatings showed that composite coatings exhibited better thermal stability compared to plain NiWP deposits. From the XRD studies it was found that metastable phases such as NiP and Ni5P2 present in the composite coatings heat treated at major exothermic peak temperature. Annealed composite coatings at various temperatures revealed higher microhardness values compared to plain NiWP deposits.

Kalavati

Papers

Influence of particle size on the microstructure, hardness and corrosion resistance of electroless Ni–P–Al2O3 composite coatings

Surface morphology and structure of electroless ternary NiWP deposits with various W and P contents

Electroless ternary Ni-W-P alloys containing micron size Al2O3 particles