Microstructure and mechanical properties of high nitrogen steel - high strength steel bimetallic multi-layered steels fabricated by plasma-arc additive manufacturing

Three bimetallic multi-layered steel samples with different structures as well as a pure high nitrogen steel (HNS) sample and a pure high strength steel (HSS) sample were fabricated by plasma-arc additive manufacturing. The microstructure and mechanical properties of the samples were characterized by various methods. The results indicated that the microstructures of HNS and HSS are mainly austenite and martensite, respectively, and the grains in the interface area of HNS and HSS grew orderly compared with the inner area. The microhardness of the HSS sample (480.7 HV-499.2 HV) is higher than that of HNS (326.4-345.1 HV), and that of the bimetallic multilayered steels is consistent with the structure distribution. The bimetallic multi-layered steels combined the tensile property advantages of HNS and HSS well, and steels with both high strength and toughness were obtained.