2019 Volume 60 Issue 6 Pages 1096-1102
Novel ferritic stainless steel with advanced mechanical properties and significant magnetic responses was prepared by a selective laser melting (SLM) process from UNS S32707 hyper-duplex stainless steel (HDSS) powder prepared by a plasma rotating electrode process (PREP). The microstructure, mechanical properties, and soft magnetic properties of the sintered state were studied. The results show that ferritic stainless steel with a relative density of 98.2% (with the theoretical density of 7.8 g/cm3) can be prepared by SLM with a laser energy density of 87.96 J/mm3 and 67° of rotation of the upper and lower layers. The rapid cooling after sintering inhibits the formation of austenite, and the ferrite content reaches 98.5%. Sintered parts prepared by SLM have excellent mechanical properties. The measured tensile strength, yield strength, and the microhardness were 1493 MPa, 1391 MPa, and 528.7 HV, respectively. The nitrogen content decreased by 33% during SLM. Nitrides precipitated at ferrite grain boundaries lower the ductility and toughness of sintered parts prepared by SLM. The measured elongation, the reduction of area, and the impact absorbing energy were 13.2%, 24.1%, and 18 J, respectively. The high ferrite content causes sintered parts prepared by SLM to have excellent soft magnetic properties. The specific saturation magnetization and the coercivity were 106 Am2/kg and 1.79 mT, respectively. This provided a new approach for the near net shaping of structural and functional integrated soft magnetic materials with both strength and corrosion resistance.
