Research On 3D Printing Process And Post-processing Of 316L/POM Composite

Metal 3D printing can quickly produce metal parts with complex shapes that cannot be achieved by traditional machining methods,and it doesn't need molds and has no excess material loss during processing,so it has great application prospects.However,traditional metal 3D printing methods demand expensive equipment,expensive materials and they possess low forming efficiency.The influence rules of printing parameters,catalytic debinding parameters and sintering parameters on the new metal 3D printing technology based on Fused Deposition Modelling(FDM)combined with FDM printing,catalytic debinding and sintering were explored in this thesis.The main researches are as follows:(1)The effects of nozzle temperature,printing platform temperature,line width,contour circles number,layer thickness,filling angle,filling ratio and filling pattern on the mechanical properties of the printed parts were studied.The results show that contour circles number,layer thickness,filling ratio,and filling pattern have a greater effect on the tensile strength of the printed parts.The larger the contour circles number and the filling ratio,the higher the tensile strength.The thicker the layer thickness,the higher the tensile strength,but the worse the interlayer adhesion,so when the layer thickness is 0.3mm the tensile strength is lower than when it is 0.2mm.Filling patterns of concentric,linear,and honeycomb exhibit higher tensile strength,while the filling patterns of hibbert curves,archimedes curves,and octagonal spirals have lower tensile strength.The tensile strength of the printed 316L/POM FDM parts are lower than that of FDM printed pure material parts.The printed 316L/POM FDM parts aren't suitable for direct use as structural parts,but as semi-finished product,it can meet the needs of transportation and mobility.(2)The effects of catalytic debinding parameters such as debinding temperature,catalyst flow rate,debinding time and size of specimens on the catalytic debinding ratio were studied.The catalytic debinding ratio increased with the increasing of debinding temperature,catalyst flow rate,debinding time,thickness and filling ratio of specimens,but the plane size of the specimens had little effect on the catalytic debinding ratio.When the filling ratio is 100%,the debinding temperature is 130?,and the nitric acid flow rate is 0.35ml/min,the catalyst debinding rate reaches 6mm/h.(3)The effects of sintering temperature,soaking time and heating rate on the final metal parts were studied.The debinded parts shrink uniformly in all directions during the sintering process.The higher the sintering temperature,the longer the soaking time or the lower the heating rate,the larger the dimensional shrinkage and higher density,the smaller and fewer internal pores.The metallographic structures of the metal parts are austenite and Fe Ni phase.The mechanical properties of the final metal parts increase with the increase of the sintering temperature,extend of soaking time or reduce of the heating rate.When the sintering temperature is 1350?,the soaking is 2h and the heating rate is 1.5?/min,the micro hardness is 203.9HV and the tensile strength reaches 420.3MPa.The sintering temperature is one of the main factors affecting the corrosion resistance of the specimens.When the sintering temperature is 1250?,the corrosion resistance is the best,and the worst is at 1200?.