| Fused deposition modeling（FDM）is both rapid prototyping technology and additive manufacturing technology,which is most widely used in 3D printing technology.However,due to its heating mode,the printing materials of FDM are generally engineering plastics with low melting point such as ABS and PLA,and cannot directly print metal materials with high melting point.In this paper,FDM 3D printing technology,catalytic debinding technology and high-temperature sintering technology are combined to form a composite forming technology,which can realize the processing and forming of 316L stainless steel parts based on FDM.Taking Ultrafuse 316L as the printing wire,this paper studies the effects of FDM printing parameters,catalytic debinding and high temperature sintering process on the forming properties of parts.The specific contents are as follows:（1）The effects of printing temperature,printing line width,printing speed and delamination thickness on the surface quality of Ultrafuse 316L formed parts were studied.It is found that too low printing temperature makes the fuse bonding quality worse,and the surface of formed parts fluctuates.Increasing the printing temperature can reduce the surface roughness.When the printing line width is too small,the metal particles on the surface of formed parts are unevenly distributed,while the excessive printing line width will reduce the filling area and make the surface uneven.If the printing speed is too slow,the high temperature at the nozzle will be transmitted to surface of formed parts,resulting in large flatness error.If the printing speed is too fast,the consumables will be separated from the platform,resulting in printing failure.The delamination thickness has little effect on the surface morphology and roughness of formed parts.Through the orthogonal experiment of four factors and three levels,the process combination with the best dimensional accuracy is obtained by range analysis:240℃ printing temperature,0.4mm printing line width,30mm/s printing speed and 0.2mm layered thickness.（2）The effects of catalytic gas flow rate,debinding time and debinding temperature on the debinding effect of green billet were studied.The larger flow rate of catalytic gas and the longer debinding time,the better debinding quality and the higher debinding rate;Increasing the debinding temperature can also improve debinding rate,but a higher debinding temperature will decompose the auxiliary binder as the skeleton support and reduce the strength of debinding blank.（3）The effects of sintering temperature,holding time and sintering atmosphere on the formability of 316L parts were studied.With the increase of sintering temperature and holding time,the size shrinkage and density of parts increase continuously.The size shrinkage and density of sintered parts in N2 atmosphere are slightly smaller than that in vacuum atmosphere.The higher sintering temperature,the more uniform melting and bonding of metal particles and the lower surface roughness;Holding time has little effect on surface roughness;The surface of sintered parts in N2 atmosphere is rough.Under different sintering processes,the phase composition of sintered parts is austenite;The higher sintering temperature and the longer holding time,the smaller internal porosity of sintered parts,the porosity of sintered parts is slightly larger in N2atmosphere.The higher sintering temperature,the higher micro-Vickers hardness,yield strength,tensile strength and elongation after fracture of the sintered parts;The sintered parts in N2atmosphere have higher strength,but poor plasticity;Holding time has little effect on the mechanical properties of sintered parts. |
