Microstructure And Properties Of 316L Stainless Steel Fabricated By Wire Arc Additive Manufacturing

316L stainless steel is widely used in the nuclear,medical and chemical industries for its excellent machinability,weldability,mechanical properties and high corrosion resistance.Due to the high deposition rate,wire arc additive manufacturing(WAAM)has been attempted to apply to manufacturing components.However,there are still some challenges for the application of WAAM owing to the fast cooling rate and complicated cycle-heat effects.During WAAM,the effects of processing parameters on the microstructure,mechanical properties and corrosion properties are not clear.In this paper,by employing optical microscope(OM),scanning electron microscope(SEM),micro-hardness tests,tensile tests and electrochemical corrosion tests,the influences of linear heat input(LHI),cooling rate(CR)and inter-layer temperature on the microstructure,mechanical properties and corrosion properties of wire arc additive manufacturing 316 L stainless steel are investigated.Firstly,the effects of wire feed speed(WFS)and travel speed(TS)on the forming quality,geometric dimension of the single deposited layer are studied.With the increase of TS or the decrease of WFS,serpentine beads and humps are observed on the deposited layers in turn,and the depths,widths and heights of the molten pools decrease.The minimum depth of the molten pool is 0.57 mm.The working envelope of 316 L stainless steel is established by comprehensive analysis of the results.Secondly,the microstructure,mechanical properties and corrosion properties of the studied steel are revealed.The microstructures of the studied steel are composed of austenite dendrites and ?-ferrite.With the increase of LHI,the austenite primary dendrites spacings increase and the elongation rates to fracture of the tensile specimens increase.While the ultimate tensile stresses(UTSes),yield stresses(TSes)and corrosion properties of the studied steel decrease.With the CR increased,the UTS,TS and elongation to fracture of the studied steel increase due to the decreasing austenite primary dendrites spacings and the increasing ?-ferrite contents.Finally,the mechanical properties and corrosion properties of the studied steel with different inter-layer temperatures are evaluated by tensile tests,cyclic polarization tests and electrochemical impedance spectroscopy.The results show that the secondary dendrites spacings increase with the increasing inter-layer temperatures,while ?-ferrite contents are in an opposite trend.Moreover,when the inter-layer temperature is 400 °C,the surface roughness of the studied steel is 0.8 mm,and the tensile properties and corrosion properties of the studied steel are good.