Electrodeposition of Iron with Co-deposition of Carbon: On the Nature of Nanocrystalline Fe-C Coatings

Fe-C coatings were electrodeposited from an iron-sulfate electrolyte containing citric acid as a carbon source. Differently thick coatings were deposited onto amorphous substrates, which allows substrate-unbiased nucleation and thereby enables the study of the intrinsic growth of Fe-C coatings. The internal structure of the Fe-C coating was systematically investigated applying complementary methods of materials characterization using microscopy, spectroscopy, and X-ray diffraction analysis, which was further supplemented with microhardness measurements. For the measured high carbon concentration of more than 0.8 wt pct, the experimental results indicate the formation of Fe₂C carbides. Together with the nanocrystalline carbon-free ferrite grains with strong 〈311〉 fiber texture, the carbides provide a very high microhardness of almost 800 HV, as measured for the Fe-C coatings independent of the coating thickness. The results essentially contribute to understanding of the growth characteristics and phase formation during electrodeposition of the Fe-C coatings, which is needed for their industrial applications as hard coatings.