Research On Laser Additive Manufacturing Process Of 316L Stainless Steel With Wire For Inclined Wall Unsupported Structure

Inclined wall structure is a common part of complex structural parts,it is difficult to design the support body of metal additive manufacturing,and because of the different process parameters and material composition,the support body design is difficult to have universality.The support of metal additive manufacturing is heavy and difficult to fix,and requires high heat resistance and deformation resistance,the later removal of the support is relatively cumbersome,which affects the production efficiency.The research on the laser fuse additive manufacturing of inclined wall unsupported structure is of great significance for forming structural parts.At the same time,in the laser fuse additive manufacturing of the inclined wall without support structure,the supporting force gradually decreases with the increase of the inclination angle,which provides basic reference data for space microgravity additive manufacturing.Therefore,this paper built an experimental platform for laser fuse additive manufacturing with a controllable tilt angle,and carried out research on the laser fuse additive manufacturing process of 316 L stainless steel inclined wall unsupported structure.The main work is as follows:Based on the forming law and process window of laser fuse additive manufacturing,it is very important to study the laser fuse additive manufacturing process.Through the three key process parameters of wire feeding speed,scanning speed and laser power,the forming morphology and forming size of single-channel single-layer accumulation are studied,the forming law of laser fuse additive manufacturing is explored and a good forming process window is obtained.As the wire feeding speed increases,the melting height and width increase,as the scanning speed increases,the melting height and width decrease,and as the laser power increases,the melting width increases and the melting height decreases slightly.The wire feeding speed is 2.6 m/min,the scanning speed is 0.012 m/s,and the laser power is 3500 W,the shape of the single-pass single-layer accumulation is better.By studying the fluid behavior of laser fuse additive manufacturing at an oblique angle,it is found that as the number of stacked layers increases,the heat accumulation between layers increases,and the size of the molten pool increases greatly.Affected by gravity,the inclined downward flow tendency of the molten pool is strengthened,causing slight local bulges and depressions in the morphology of the lower side of the deposit.There are mainly problems of flow and hump in the process of accumulation.The formation period of hump is between 415 and 901ms,and the height of hump is between 3 and 4 mm.The behavior characteristics of hump are observed and analyzed,and the formation mechanism of hump is revealed.Through process optimization,the heat input and wire feeding speed are reduced,and the temperature field of the laser fuse additive manufacturing process is studied by finite element simulation.Controlling the cooling time of the interlayer accumulation to 100 s realizes the excellent manufacturing of a single-channel 10-layer sloping wall unsupported structure accumulation body.The structure of the accumulation body is composed of a large number of columnar crystals with small crystal grains,and the width of the columnar crystals is between6.2 and 9.2 μm.The accumulation body has excellent mechanical properties,the hardness distribution in the middle area is high and average,and the average hardness is 191 HV.The transverse tensile strength is 638 MPa,and the elongation is 50%,which is higher than the316 L as-cast sample with the same chemical composition.