Research on microstructure and properties of 304 stainless steel made by MIG filler additive manufacturing

Abstract

In this paper, the MIG wire-filling method was used to fabricate 304 stainless steel in a layer-by-layer filling manner on a 20 mm thick low carbon steel surface. The microstructures of the upper, middle and lower parts of the cladding layer under different heat input conditions were studied. Finally, the microhardness test was carried out on different heights of the cladding layer produced by additive manufacturing under different processes. The results showed that with the gradual reduction of heat input, the grains of the same characteristic area were gradually refined under different processes. The cladding layer structure was mainly composed of columnar crystals, dendrites and equiaxed crystals. The microhardness increased as the heat input decreased. In this paper, the highest hardness value was 257.8 HV. The process parameters were voltage 27 V, current 190 A, deposition speed 8.69 mm/s, wire feeding speed 7 m/min, wire feeding angle 90° and shielding gas flow rate 15 L/min, respectively.