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.