Cobalt-Tungsten (Co-W) alloy coatings possessing high hardness and wear/corrosion resistance, due to their ecofriendly processing, have been of interest to the researchers owing to its various industrial applications in automobile, aerospace, and machine parts. This technical paper reports Co-W alloy coatings dispersed with multiwalled carbon nanotubes (MWCNTs) produced by pulse electrodeposition from aqueous bath involving cobalt sulfate, sodium tungstate, and citric acid on stainless steel substrate (SS316). Studies on surface morphology through SEM, microhardness by Vickers method, microwear by pin-on-disk method, and corrosion behavior through potentiodynamic polarization method for the Co-W-CNT coatings were reported. Characterization studies were done by SEM and EDX analysis. The results showed that the corrosion and tribological properties of the pulse-electrodeposited Co-W-CNT alloy coatings were greatly influenced by its morphology, microhardness, %W, and MWCNT content in the coatings.

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Plasma-sprayed NiCrBSi-graphite coatings have been subjected to solid particle erosion at elevated temperatures. The work reports the erosion resistance of NiCrBSi coatings with 4, 6 and 8 wt-% addition of graphite and optimum graphite content for erosion resistance. The coatings were analyzed using optical microscopy, XRD and scanning electron microscopy. Testing was carried out using air-jet erosion test rig, at an impact velocity of 70 m s−1 and at 45°and 90°angles with sand flow rate of 1 g min−1 at RT, 500°C and 650°C. Morphology of eroded surface shows crater, lip, groove formation and chipping as visible mechanism of material removal. Coating with 4wt% distribution of graphite exhibits higher erosion resistance as compared to the coating without graphite addition and improved microhardness. Microstructure images reveal that increase in graphite content above 4% results in the segregation of graphite and leading to soft islands in the coatings thereby decreasing the erosion resistance.

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Nanocrystalline cobalt-phosphorus-carbon nanotube (CNT) composite coatings on stainless steel substrates with various contents of phosphorus were prepared by a pulse electrodeposition technique involving cobalt plating bath dispersed with CNTs. Microhardness, potentiodynamic polarisation and scanning electron microscopy (SEM) studies were used to characterise Co-P and Co-P-CNT composite coatings. The microhardness of Co-P-CNT coatings is found higher than that of Co-P coating. With the increase in phosphorus content, the microhardness values for the heat treated coatings increased almost twice when compared to that of the as deposited coatings. The effects of various contents of phosphorus and CNTs on the corrosion resistance were investigated, and it was found that nanocrystalline Co-P composite coatings exhibit better corrosion resistance than Co-P-CNT coatings.