Anisotropic Mechanical Properties Of 316L Stainless Steel Fabricated By Plasma Arc Additive Manufacturing

Additive manufacturing(AM),also known as 3D–printing,is an advanced manufacturing technology.Compared with traditional manufacturing methods,AM has the advantages of no mold,fast,near net shape.In order to make AM materials have a large application in industries,it is important to study the mechanical properties especially for the fatigue property.This topic is based on plasma arc,and 316L stainless steel wire is used as the material for additive manufacturing(PAM).Firstly,the orthogonal test method was used to study the effects of welding current,deposition speed and wire feeding speed on surface forming and macroscopic size for the deposited single pass.According to the optimal parameters,a 316L stainless steel bulk was fabricated.Samples were machined along the scan direction(SD),45°to the SD(45°)and built direction(BD).The microstructures were observed by optical microscopy(OM),scanning electron microscopy(SEM)and electron backscattered diffraction(EBSD).Uniaxial tensile tests and uniaxial fatigue tests were carried out in ambient air to analyze the difference between different direction samples.And the relationships between microstructures and mechanical properties anisotropy was analyzed by combining the microstructures and mechanical properties.The main conclusions are as follows:The influence order of the different process parameters on the deposited single pass weld width is:welding current>deposition speed>wire feeding speed;for deposited single pass height is:wire feeding>speed welding current>deposition speed;and for width height ratio is the same as deposited single pass height.The optimal track spacing is 4.5 mm.Both the tensile and fatigue properties of the SD and 45°samples are nearly the same and higher than those of BD samples.The fatigue strengths of the three directions at 10~6 cycles are170 MPa,180 MPa and 140 MPa,respectively,which is inferior to the 316L stainless steel obtained by the conventional manufacturing methods.The anisotropy of materials produced by additive manufacturing is mainly due to the directionality of microstructures and the shape of defect.The unique microstructure of additive manufacturing has a positive effect on the improvement of mechanical properties,while the presence of defects is not good for the improvement of mechanical properties.The effects of defects on fatigue performance is far greater than the influence on tensile properties and shock resistance.The tensile properties can reach the level of forging components,while the fatigue properties are much lower than the forging components.A model was used to predict the fatigue life and the predicted results show a good agreement with the experimental data.