Morphological Studies of Electrodeposited Cobalt Based Coatings: Effect of Alloying Elements

摘要

Electrodeposition is known as a simple and low-cost method to synthesize good-quality coating with excellent hardness. In this work, the morphology changes on Cobalt coating with the addition of iron and nickel elements were investigated. Co (Cobalt) and Co-based alloy coatings were prepared by electrodeposition technique using sulfate-based electrolytes. The process was conducted at 50°C temperature in an acidic environment (pH 3). The pure Co coating shows the tendency to form snowflake-like morphology structure. The dendritic morphology appeared in the Co-Fe coatings. However, the dendritic morphology was totally disappeared in the Co-Ni-Fe morphology and replaced by spherical morphology. The crystal structure of Co-Ni-Fe coating changed from bcc into mixed bcc+fcc structure with the addition of Ni element in Co-Fe composition. The Ni element which had been introduced in the Co-Fe composition improved the surface morphology and reduced the average particle size. The surface morphologies in the coatings affect the particles size and hardness property. This may due to the formation of full, compact coatings morphology and introduction of particles boundaries interphase. The Co-Ni-Fe coating with smaller particle size, less void formation and mixed crystal structure of bcc + fcc was roughly two times harder than pure Co.