Thermal evolution of ferrite in electrodeposited iron‑carbon coatings in relation to phase transformations during post-deposition annealing

Repair of damaged surfaces with hard iron-carbon coatings

“…Figure 1 shows examples of microscopy investigations of as-deposited iron-carbon coatings that exemplify the fine grained microstructure. As typical for electrodeposited coatings and consistent with the nanocrystalline grains that were quantified previously [4,7,11], LOM cannot resolve the microstructure and only allows the evaluation of the coating thickness and its uniformity (Figure 1a). Neither SEM can resolve the nanocrystalline grains, although it suggests a columnar morphology (Figure 1b).…”

“…Neither SEM can resolve the nanocrystalline grains, although it suggests a columnar morphology (Figure 1b). This is verified by TEM (Figure 1c), and high-resolution TEM (Figure 1d) reveals that individual grains of as-deposited coatings possess dimensions below 20 nm and below 50 nm, respectively, for the width and length of the columnar grains, which is further confirmed by X-ray diffraction analysis [7,11].…”

“…Several iron-carbon coatings have been deposited at various deposition times resulting in a wide range of coating thicknesses from below 10 µm up to 360 µm. For all of these coatings, the same morphology as described above (nanocrystalline, columnar grains) was observed [4,7,11], but this should not be of further interest for the present manuscript and rather the homogeneity of the deposited coating thickness is addressed here. An interesting observation is revealed from the cross section analysis of differently thick iron-carbon coatings deposited onto an amorphous Ni-P layer, see example in Figure 1a for a coating thickness of 58 µm.…”

“…Both would result in a rather complex deposition process when applied for iron-carbon coatings, which even more complicates the understanding of as-deposited coatings, and it would require considerable extra efforts for industrial applications, in terms of either the complex maintenance of an additive containing electrolyte or the setup of optimized pulse plating parameters. Based on previous extensive materials characterization toward the understanding of the internal structure of electrodeposited iron-carbon coatings [4,6,7,11], it is presumed that the growth of an iron-carbon coating provides levelling on-its-own. This is considered relevant for industry, because it opens up for the repair of damaged surfaces without the need to remove coating relicts from previous surface treatment and it avoids a complete re-deposition of the whole coating or even the replacement of a worn component.…”

Identification of carbon‐containing phases in electrodeposited hard Fe–C coatings with intentionally codeposited carbon

“…Driven by the urgent need for a sustainable, environmentally friendly alternative to hard chrome coatings, the ability to deposit particularly hard and wear resistant iron-based coatings has been demonstrated, and promising mechanical properties are reported for the electrodeposition of ironcarbon coatings. [1][2][3][4][5][6][7] Despite the technological importance of ironcarbon bulk alloys (e.g., steels), the intentional codeposition of carbon from iron-based electrolytes has not gained much attention yet, and carbon in electrodeposited coatings is often either disregarded or called an impurity. 8,9 Typical electrolytes for electrodeposition of iron, for example, iron sulfate-based solutions, usually include citric acid or citrates, which are added primarily due to their role as complexing agents, as buffers, or to enhance the electrolyte stability.…”