Аңдатпа
Introduction. The manufacture and restoration of mining equipment components require materials combining high hardness, wear resistance, corrosion resistance, and sufficient technological properties for subsequent machining. Wire-based additive manufacturing provides opportunities for producing near-net-shape components and restoring locally worn regions while reducing the amount of material removed during subsequent processing. However, the properties of martensitic stainless steels produced by additive manufacturing are strongly dependent on thermal history, including heat input, cooling conditions, repeated reheating, and build orientation. This study investigates the influence of thermal conditions during wire-based additive manufacturing of 40Cr13 martensitic stainless steel on its microstructure and hardness, with particular emphasis on its potential application to components of mining machinery. Methods. Experimental samples of 40Cr13 steel were produced using electron beam additive manufacturing (EBM) and wire arc additive manufacturing (WAAM). Vertical and horizontal build orientations were investigated to evaluate the influence of heat dissipation conditions. For EBM, the vertical specimens were produced at an electron beam current of 21 mA and a wire feed rate of 1050 mm/min, whereas the horizontal specimens were produced at 30 mA and 700 mm/min, respectively. The deposited material was examined using optical and scanning electron microscopy, and hardness was determined using the Vickers method. Numerical modeling of transient temperature fields was additionally employed to analyze cooling rates, heat accumulation, and repeated thermal cycles occurring during layer-by-layer deposition. Experimental observations were compared with the calculated thermal histories to establish relationships between process conditions, phase transformations, microstructure, and hardness. Results. The results demonstrated a pronounced influence of build orientation and heat dissipation on the properties of additively manufactured 40Cr13 steel. The average hardness of horizontally built EBM specimens reached approximately 576 HV, compared with approximately 525 HV for vertically built specimens. The difference was 51 HV, corresponding to an increase of approximately 9.7% relative to the vertical configuration. The higher hardness of horizontally deposited material was associated with more intensive heat transfer to the substrate, reduced heat accumulation, and conditions favorable for retaining a predominantly martensitic structure. Microstructural examination revealed a dense material containing predominantly needle-like martensite with retained austenite and without pronounced interlayer cracking. Comparison of the two additive technologies showed that EBM provided more localized thermal exposure and more favorable conditions for obtaining a relatively homogeneous structure, whereas WAAM offered higher deposition productivity but was characterized by greater heat accumulation and a wider thermally affected region. Numerical analysis confirmed that repeated heating of previously deposited layers may cause martensite tempering and, at sufficiently high temperatures, repeated austenitization followed by martensitic transformation during cooling. Conclusions. The study demonstrates that thermal conditions are a key factor controlling the microstructure and hardness of wire-based additively manufactured 40Cr13 steel. The established relationship between process parameters, heat dissipation, thermal cycles, phase transformations, and hardness provides a basis for selecting rational EBM and WAAM processing conditions. EBM is preferable when localized thermal exposure and structural uniformity are required, whereas WAAM is particularly promising for high-productivity manufacturing and restoration of large components, provided that heat input and interlayer temperature are carefully controlled. The obtained results can be used in the development of additive manufacturing and repair technologies for shafts, axles, pump components, and other mining machinery parts requiring a combination of high hardness, wear resistance, and corrosion resistance.