Microstructures and mechanical properties of ultra-high strength steel 300M fabricated by laser melting deposition

Thin plates of ultra-high strength steel 300M were fabricated by the laser melting deposition manufacturing process. Microstructure of the steel 300M was characterized by OM and SEM. The mechanical properties at ambient temperature of the steel were tested. The results show that the as-deposited steel has a rapidly solidified fine cellular dendritic structure with a mixed martensite-bainite microstructure because of high temperature gradient and cooling rate during the laser melting deposition process. The tensile properties at room temperature are comparable to the level of forging.