Manufacturing Fe–TiC metal matrix composite by Electron Beam Powder Bed Fusion from pre-alloyed gas atomized powder

Abstract

Fe–TiC metal matrix composite (MMC) material is fabricated by EB-PBF (Electron Beam Powder Bed Fusion) additive manufacturing technique. Herewith, gas atomized model alloy powder containing in-situ formed reinforcement phase is utilized. Powder properties (i.e., particle size distribution, morphology, flowability, tap, and apparent density) are discussed in relation to composite powder applicability for EB-PBF. As a result, samples with over 99% density were fabricated. Cross-section samples investigated via SEM (scanning electron microscopy) and EBSD (electron back-scattered diffraction analysis) reveal homogeneously distributed submicron TiC reinforcements of two morphologies – blocky TiC precipitates and fine needle-shaped ones. Fabricated composite demonstrates enhanced tensile strength of 537 MPa, while preserving the sufficient level of ductility (35.0%), which correlates with the low hardness of 153.9 HV10. Additionally, heat treatment of as-built samples is investigated by implementing differential scanning calorimetry (DSC), dilatometry analysis, and austenitization-water-quenching techniques. Applied heat treatment induces a significant grain refinement, which increases the hardness of treated samples up to 246.3 HV10 by water quenching, while TiC precipitates undergo minor changes in morphology and size. Fabricated MMC material demonstrates the successful application of the gas atomized powder with an in-situ formed carbide reinforcement phase for additive manufacturing.