Abstract
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.
Highlights
Electroless nickel coating has received widespread acceptance as it provides a uniform deposit on irregular surfaces, direct deposition on surface-activated nonconductors, formation of less porous deposits, and high hardness and excellent resistance to wear, abrasion, and corrosion [1, 2]
The surface of the coating consists of relatively lower amount of nickel particles on the matrix and nonuniform deposition of nickel resulted in higher surface roughness
The electroless Ni–P coatings produced with addition of nanoadditivesss with sodium lauryl sulphate (SLS) surfactant in the EN bath lowered the friction coefficient upto 52.38% and 61.90% with the addition of nano Al2O3 and nano SiO when compared to the coatings produced without nanoadditivesss
Summary
Electroless nickel coating has received widespread acceptance as it provides a uniform deposit on irregular surfaces, direct deposition on surface-activated nonconductors, formation of less porous deposits, and high hardness and excellent resistance to wear, abrasion, and corrosion [1, 2]. The quality of obtaining electroless Ni–P deposit on the substrate depends on many factors such as temperature, pH of bath, bath loading, concentrations of nickel and the reducing agent, and the surface properties of the substrates [14,15,16]. Wetting agents, such as ionic and nonionic surfactants, are often added to increase the wettability of coated surfaces [17]. Despite the complicated behaviour of the deposition reactions, qualitative discussions on the effects of added nanoadditivesss such as Al2O3, SiO, and ZnO in the presence of surfactant (SLS) the surface roughness, surface morphology, microhardness, specific wear rate, and wear morphology are investigated and reported in this paper
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