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In the present work, tungsten carbide (WC) particulate of average size 10 mm were electrocodeposited in the nickel metal matrix, to form metal matrix composite (MMC) coating over the EN8 steel substrate. The electrodeposition of Ni-WC particulate composite coating was carried out using the Watt's bath under the influence of varying current density and duty cycle. It was found that current density of 0.02 A/ cm 2 was sufficient to start the codeposition kinetics. But, good quality of electrodeposition was obtained at a current density of 0.04 A/cm 2 . The WC particulate entrapment and distribution of WC particles in Ni matrix according the variation in experimental parameters has been reported. The dense and compact microstructure was obtained at a current density of 0.04 A/cm 2 and duty cycle of 30%. Microhardness and corrosion resistance properties of composite coating were also evaluated and reported. INTRODUCTIONSurface modification, with the formation=deposition of overlaying layer of metal matrix composite (MMC), provides enhanced mechanical, tribological, and corrosion resistance properties. During the last few decades, researchers have attempted to improve those properties through electrocodeposition of hard particles such as Al 2 O 3 [1-4], TiO 2 [5, 6], SiC [7-9], ZrO 2 [10, 11], WS 2 [12], and Si 3 N 4 [13,14] in different metal matrixes (Ni, Cr, Co, etc.). Nickel is a most suitable metal, among all metal matrixes due to its good chemical compatibility with the other metal and alloys [18]. Moreover, it imparts very good corrosion resistance property to the coated surface. Tungsten carbide is a hard ceramic having high thermal stability and good dispersion properties which lead to high wear and thermal resistance properties of the coating. Deposition of electrically nonconductive tungsten carbide particles alone is very difficult, as it produces obstruction to obtain dense interface of metal-carbide during the electrodeposition process, but it can be easily codeposited with a transition group of elements. Although there are a number of surface coating techniques available, but the electrodeposition process has drawn significant attention because it is a nonthermal process, technologically feasible, easily controllable, economically superior technique to produce a MMC. It is based on the uniform entrapment of second-phase hard particles within the metal matrix.Although many research papers have been reported in the area of WC composite coating through direct current

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In the present study, tribological properties of castor oil have been investigated with and/or without use of additives by using four-ball tester. In the base castor oil, calcium–copper–titanate nanoparticles (CCTO) and zinc dialkyldithiophosphate (ZDDP) were added in different concentrations (i.e., 0.1, 0.25, 0.5, and 1.0 w/v%) to study their individual effect on tribological performance. Tribological test results have shown that there is an improvement in the antiwear, extreme-pressure (EP) properties at 0.25 and 1.0 w/v% for both the additives, respectively. However, in the coefficient of friction (COF) test (incipient seizure load), an optimum concentration of 0.5 w/v% was observed for ZDDP additive, whereas CCTO nanoparticles have shown similar level of performance at all concentrations. The worn-out surfaces were analyzed by using different analytical tools.

The aim of the present study is to examine the antiwear, antifriction, and extreme pressure performance of castor oil with nano-additives by using a four-ball tester. CeO2 (≈90 nm) and polytetrafluroethylene (≈150 nm) nanoparticles were used as an additive in castor oil with four different concentrations in the range of 0.1–1.0% w/v. The suspension stability of the nanoparticles was improved by using sodium dodecyl sulfate as a dispersant. Different analytical tools were used to characterize the nanoparticles parameter (i.e. shape and size) as well as the worn surfaces. The additive concentration was optimized on the basis of tribological performance. The test results of antiwear and extreme pressure property have been reported on the basis of wear scar diameter and weld load, respectively. For the antiwear test, it was observed that the maximum reduction in the wear scar diameter was 37.4 and 35.3% at an optimum concentration of CeO2 and polytetrafluroethylene additive, respectively. Also, antifriction and load carrying properties of castor oil were significantly improved with the addition of nanoparticles as an additive in a small amount. The mechanism for such improvement in the tribological behavior has also been discussed.

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