Electrodeposition and tribological properties of self-lubricating Ni-BaCr2O4 composite coatings

In the present work, Ni-BaCr₂O₄ composite coatings were electrodeposited on superalloy Inconel 718 from a Watts type electrolyte containing BaCr₂O₄ particles, which were dispersed in suspension with the aid of a cationic surfactant cetyltrimethylammonium bromide (CTAB). BaCr₂O₄ particles were synthesized by solid state reaction method and had a size range of 0.8-2μm. The content of BaCr₂O₄ incorporated into composite coatings depended mainly upon the BaCr₂O₄ powder concentration in bath, cathode current density and temperature condition in the electrolyte. Microstructure and microhardness of Ni-BaCr₂O₄ composite coatings were investigated with scanning electron microscope (SEM), X-ray diffractometer (XRD) and microhardness tester. The friction and wear properties of Ni-BaCr₂O₄ composite coatings containing various amounts of BaCr₂O₄ particles were studied with a ball-on-disk friction and wear tester in sliding against alumina ball. Ni-BaCr₂O₄ composite coatings exhibits a distinctly low friction coefficient and a small wear rate as contrasted with pure nickel coating and the substrate. The wear resistance of Ni-BaCr₂O₄ composite coating electrodeposited on superalloy Inconel 718 increases with increasing BaCr₂O₄ content. The wear mechanisms of Ni-BaCr₂O₄ composite coatings were proposed as contrasted with pure Ni coatings and the superalloy substrate at identical wear conditions.