Preparation of 24CrNiMoY alloy steel with high strength and toughness by selective laser melting

24CrNiMoY alloy steel with high strength and toughness was prepared by selective laser melting (SLM) technology. The microstructure and mechanical properties of alloy steel samples prepared by SLM using different laser energies were studied. The results showed that with increasing energy density, the internal defects of the sample first decreased and then increased, and the hardness and tensile properties also showed a trend of increasing at first but decreasing afterwards. When the energy density was 100.7 J/mm 3 , the alloy steel sample has the fewest defects and the highest hardness (391.2 HV 0.2 ). The tensile strength and impact toughness also reached the best state: the tensile strength was 1252.83 MPa, the yield strength was 1041.62 MPa, the elongation to fracture was 12.89%, and the impact toughness was 65.7 J. The microstructure of 24CrNiMoY alloy steel prepared by SLM is mainly composed of fine lath martensite, which has good strength and toughness.