R. Rajendran

Bio: R. Rajendran is an academic researcher from SRM University. The author has contributed to research in topics: Coating & Indentation hardness. The author has an hindex of 6, co-authored 20 publications receiving 165 citations. Previous affiliations of R. Rajendran include B. S. Abdur Rahman University & Crescent University.

Effect of surfactants on the coating properties and corrosion behaviour of Ni–P–nano-TiO2 coatings

Abstract: In this paper, the effects of two different types of surfactants on the properties of Ni–P–TiO 2 coating on low carbon steel substrate were investigated. Sodium dodecyl sulphate (SDS) — anionic surfactant and dodecyl trimethyl ammonium bromide (DTAB) — cationic surfactant were used for the deposition. Deposits were characterized by a high resolution scanning electron microscope (HR-SEM), an energy dispersive X-ray spectrometer (EDS), and X-ray diffraction (XRD) to study the surface morphology, composition and crystal structure of the coatings respectively. In addition, the influence of surfactants on the corrosion behaviour of Ni–P–TiO 2 coatings was also examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% sodium chloride solution. The results showed that at an optimum concentration of cationic surfactant DTAB, uniform distribution of TiO 2 particles with no defects was observed. The corrosion properties were improved by the incorporation of TiO 2 particles in the Ni–P matrix. The increase in corrosion resistance of the Ni–P-TiO 2 coatings significantly depends on the surfactant and its concentration.

Phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on cast aluminium LM24 alloy substrate

Abstract: Electroless Ni–P (EN) and composite Ni–P–SiC (ENC) coatings were developed on cast aluminium alloy substrate, LM24. The coating phase composition, microstructure and microhardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester, respectively, on as-plated and heat-treated specimens. The original microstructure of the Ni–P matrix is not affected by the inclusion of the hard particles SiC. No formation of Ni–Si phase was observed up to 500 °C of heat treatment. The microhardness is increased on incorporation of SiC in Ni–P matrix. The hardening mechanism is the formation of intermetallic phase Ni3P on annealing at elevated temperature.

Abrasive wear resistance of electroless Ni-P coated aluminium after post treatment

Abstract: Electroless nickel (EN) coatings are recognised for their hardness and wear resistance in automotive and aerospace industries. In this work, electroless Ni–P coatings were deposited on aluminium alloy substrate LM24 (Al–9 wt.% Si alloy) and the effect of post treatment on the wear resistance was studied. The post treatments included heat treatment and lapping with two different surface textures. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and micro-abrasion tester were used to analyse morphology, structure and abrasive wear resistance of the coatings. Post heat treatment significantly improved the coating density and structure, giving rise to enhanced hardness and wear resistance. Microhardness of electroless Ni–P coatings with thickness of about 15 μm increased due to the formation of Ni 3 P after heat treatment.

Effect of Reduced Graphene Oxide Reinforcement on the Wear Characteristics of Electroless Ni-P Coatings

Abstract: Electroless composite coatings with various concentrations of reduced graphene oxide (rGO) particles were deposited onto mild steel substrate. The effects of adding rGO particles by varying their concentration from 0 to 100 mg/L on morphology, composition, microhardness, adhesion, wear and friction of the electroless composite coatings were investigated. Among the various parameters that influence the tribological behavior, sliding velocity was varied within a specific range for definite concentrations of rGO to obtain enhanced wear resistance in this study. The micrographs of the worn surfaces and indented spots were examined for the nature of wear mechanism and interfacial adhesion. The wear rate increased with increasing sliding velocity but was relatively stable for coatings with lower concentrations of rGO.

Alloy Phase Diagrams

Abstract: With the presentation of a theory of liquid alloys, we have now assembled all the necessary tools for the ab initio construction of an alloy phase diagram.

A review of electrodeposited Ni-Co alloy and composite coatings: Microstructure, properties and applications

Abstract: Ni Co alloy electrodeposits have been widely employed in industry due to their good corrosion and wear resistance, high mechanical strength, moderate thermal conductivity and outstanding electrocatalytic and magnetic properties. This review aims to provide an insight into the mechanism of electrodeposition and effect of operational parameters and deposit microstructure, together with the mechanical, electrochemical and tribological characteristics of Ni Co alloys and included particle, composite deposits. Potential applications of the coatings have also been considered in applications as diverse as additive manufacturing, micro-tools, micro-sensors, electronic imaging and electrochemical energy conversion.

Electroless Ni-P-SiC Composite Coatings with Superfine Particles

Abstract: 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

A Review on the Corrosion Behaviour of Nanocoatings on Metallic Substrates

Abstract: Growth in nanocoatings technology is moving towards implementing nanocoatings in many sectors of the industry due to their excellent abilities. Nanocoatings offer numerous advantages, including surface hardness, adhesive strength, long-term and/or high-temperature corrosion resistance, the enhancement of tribological properties, etc. In addition, nanocoatings can be applied in thinner and smoother thickness, which allows flexibility in equipment design, improved efficiency, lower fuel economy, lower carbon footprints, and lower maintenance and operating costs. Nanocoatings are utilised efficiently to reduce the effect of a corrosive environment. A nanocoating is a coating that either has constituents in the nanoscale, or is composed of layers that are less than 100 nm. The fine sizes of nanomaterials and the high density of their ground boundaries enable good adhesion and an excellent physical coverage of the coated surface. Yet, such fine properties might form active sites for corrosion attack. This paper reviews the corrosion behaviour of metallic, ceramic, and nanocomposite coatings on the surface of metallic substrates. It summarises the factors affecting the corrosion of these substrates, as well as the conditions where such coatings provided required protection.