Influence of Mn Element on the Microstructure Evolution and Mechanical Properties of High-Strength Iron-Based Alloy...

Manganese can provide strong solid-solution strengthening in austenite, thereby effectively enhancing the strength and toughness of Fe-based coatings. However, the underlying mechanism remains unclear. In this study, building on previously developed high-strength, hard Fe-based alloy coatings produced via laser cladding, the influence of Mn content on the microstructural evolution and mechanical properties is systematically investigated using XRD, SEM, TEM, microhardness testing, and a reciprocating friction and wear testing machine. The results show that the coatings fabricated from three iron-based alloy powders are primarily composed of a martensitic matrix, retained austenite, and various MxC-type eutectic carbides (such as MC, M₂C, M₆C). With increasing Mn content, the MC-type carbides gradually change from a blocky morphology to a fishbone-like structure, while the originally fishbone-like M₆C-type carbides first become blocky and eventually turn into fine granules. Meanwhile, the sizes of all three types of carbides are refined. Especially, after the addition of Mn, dispersed second-phase particles (Mn-Si-O) precipitate in the coatings. The coating with 2.0 wt.% Mn exhibits the best comprehensive mechanical properties: an average microhardness of 925 ± 8 HV_0.5 and a minimum wear rate of 0.78 × 10^-6 mm³/N·m.