Microstructure and Hardness of High-Manganese Steel Coatings Reinforced with Molybdenum Carbide (Mo2C)

This study investigates the formation of the microstructure and phase composition of hardfacing coatings based on the high-manganese steel–Mo 2 C system, produced by flux-cored arc welding (FCAW). A combination of thermodynamic modelling using Thermo-Calc software and experimental characterization via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) was employed. The results indicate that the system is of a eutectic type, with the Mo 2 C-based carbide phase crystallizing as a network of thin layers surrounding the primary austenite grains, in contrast to the discrete particle morphology seen with other carbides like NbC and TiC. This carbide network morphology was found to inhibit the strain-hardening capacity of the austenitic matrix. However, the addition of Mo 2 C effectively suppressed the formation of cementite and led to a significant increase in the as-deposited hardness, from ~20 HRC to ~35 HRC with 20 vol.% Mo 2 C. The findings suggest that these coatings are suitable for applications involving high static and dynamic contact loads where initial hardness is more critical than work-hardening potential.