Tribological Properties of Flame-Sprayed Fe-Based Composite Coatings Synergistically Enhanced by NiCr-Cr₃C₂ and...

Moving parts in mechanical equipment are susceptible to wear under sliding friction, which can reduce service life and operational reliability. Although Fe-based alloy coatings provide high hardness and relatively low cost, their friction-reduction capability remains limited, while direct incorporation of solid lubricants may result in thermal decomposition and phase transformation during high-temperature spraying. In this study, a Fe-based composite coating was designed using Fe60 as the matrix, NiCr-Cr₃C₂ as a wear-resistant reinforcing phase, and Ni-coated MoS₂ as a source of Mo/S-containing lubricating components. The coatings were fabricated by flame spraying, and the effects of composition on their microstructure, phase constitution, hardness, and tribological properties were systematically investigated. The results show that MoS₂ undergoes substantial thermal transformation during spraying, accompanied by the formation of Mo- and S-containing phases. The tribological behavior was further evaluated by combining friction and wear measurements with worn-surface SEM/EDS, XRD, and two-dimensional cross-sectional wear-track profiles. Among the nine investigated formulations, the coating containing 15 wt.% Ni-MoS₂ and 40 wt.% NiCr-Cr₃C₂ (C6) exhibited the lowest measured friction coefficient of 0.50 and a wear rate of (0.59 × 10^-4) mm³/(N·m), together with the highest measured microhardness. The relatively shallow wear-track profile of C6, together with the retention of Cr/Ni-rich hard phases and the presence of Mo/S-containing species on the worn surface, supports an evidence-based interpretation in which the Cr₃C₂-containing phase provides load-bearing and wear resistance, the Mo/S-containing products may contribute to reducing interfacial shear resistance, and the Fe60 matrix provides continuous support and accommodates local deformation. These complementary effects contribute to the composition-dependent balance between friction reduction and wear resistance. The present findings provide a compositional reference for designing thermally sprayed Fe-based composite coatings with combined wear resistance and friction-reduction capability under the investigated dry-sliding conditions.