Microstructure and mechanical properties of bimetallic intertexture structure fabricated by plasma arc additive manufacturing

Using 18Ni high strength steel and high nitrogen austenitic stainless steel as wires, bimetallic intertexture structure of high strength steel and high nitrogen steel was fabricated by plasma arc additive manufacturing. The microstructure and mechanical properties of bimetallic intertexture structure of high strength steel and high nitrogen steel were studied by microstructure observation, microhardness and tensile strength test. The results indicate that the microstructure in high nitrogen steel region are mainly equiaxed crystals and dendrite of austenite, the microstructure of high strength steel area is lath martensite. The hardness of the high strength steel area varies from 480 to 500 HV, the hardness of high nitrogen steel area varies from 310 to 320 HV. The tensile test results show that the average tensile strength of the intertexture structure in the x direction is 1 092 MPa, which is slightly less than the tensile strength in the y direction of 1 189 MPa. The average elongation after fracture in the x direction is 20.0%, which is not much different from the elongation after fracture in the y direction which is 19.5%. The fracture presents dark gray and obviously fibrous, with a large number of equiaxed dimples distributed, the dimples are large and deep, and there is an obvious shear lip area on the edge of the fracture, which is a ductile fracture.