Structure and morphology of composite coating of chromium with diamond nanoparticles on sintered steels

Abstract

Electrochemical chromium coatings modified with diamond nanoparticles (ND) were deposited on sintered steel materials obtained from iron powder and ultrafine graphite powder. The diamond nanoparticles were produced by detonation synthesis. Their average size is 6 nm. The sintered steel consisted of 0.2, 0.4, 0.6 and 0.8%C (added in the form of graphite) by weight. The produced composite coatings consisting of Cr + ND were compact, tightly adhering to the substrate, with thickness of about 25–35 μm. The surface morphology and microstructure of the coatings were investigated by SEM and EDS analyzes. The main objective of the study was to explore the presence of ND in the coating by the X-ray photoelectron spectroscopy and the impact of the ND concentration in the electrolyte on the presence of the diamond nanoparticles in the coating. The spectra of the C1s photoelectronic line were obtained, the sp3/sp2 ratio and the sp3 + sp2 sum were determined electronically on the surface of the coatings (depth 10 nm). The Cr2p photoelectronic line spectra were also obtained. The coatings were deposited from electrolytes with ND concentrations of 10, 25 and 40 g/l. A diamond-like phase has been found in coatings obtained at concentrations of diamond nanoparticles in the electrolyte of 25 and 40 g/l. The sp3/sp2 ratio with a value equal to or greater than 1.2 is an indication of the presence of a diamond-like phase in the coatings and the ratio depends on the concentration of ND in the electrolyte.