PSI - Issue 81

Pavlo Prysyazhnyuk et al. / Procedia Structural Integrity 81 (2026) 552–557

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metallic matrix to maintain its contiguity and, consequently, its ductility. At the interface with the C45 steel substrate, a well defined yet complex fusion zone approximately 10 – 15 µm thick is observed. An energy-dispersive X-ray spectroscopy (EDS) line scan confirms that the primary carbides are significantly enriched in Molybdenum (Mo) and Manganese (Mn), which is in excellent agreement with the thermodynamic predictions (Fig. 3). Furthermore, it is noteworthy that no cementite (Fe 3 C) was detected in the microstructure; its inherent brittleness would have negatively impacted the austenitic matrix's capacity for strain hardening. In summary, the analysis confirms the formation of a high-strength, in-situ composite material where the discontinuous network of hard primary carbides provides high wear resistance without creating continuous paths for crack propagation, while the absence of detrimental phases and the presence of a sound fusion zone ensure the coating's overall integrity during service. To further elucidate the elemental distribution within the hardfaced layer, energy-dispersive X-ray spectroscopy (EDS) mapping was performed (Figure 4). The resulting elemental maps provide a direct visualization of the solute partitioning between the primary carbide phase and the surrounding metallic matrix. A strong co-localization of Mo and C is clearly observed within the bright, dendritic phases of the micrograph. This spatial correlation provides compelling evidence for the formation of a molybdenum-rich carbide. The map for Mn also reveals its elevated concentration within these bright regions. This confirms that the primary carbides are a complex phase with the approximate formula (Mo,Mn,Fe) 2 C, which is in excellent agreement with the thermodynamic predictions. Conversely, the map for Fe shows a near-inverse distribution, confirming it as the primary constituent of the darker, interdendritic eutectic matrix. Si also appears to be predominantly dissolved within this iron-rich region. In summary, the EDS mapping offers definitive visual confirmation of the in-situ composite microstructure. It validates the phase identification and demonstrates the distinct chemical partitioning where carbide-forming elements (Mo, Mn, C) segregate to form a hard, reinforcing network (the bright phase), while the remaining elements (Fe, Si) solidify to form a more ductile metallic matrix (the dark phase).

Fig. 3. Microstructure of the deposited "high-manganese steel – Mo₂C" coating at different magnifications and the distribution of elements from the coating to the substrate (initial Mo₂C content in the flux ~15 vol.%).

Fig. 4. EDS maps of the elemental distribution in the deposited "high-manganese steel – Mo₂C" coating.