Research On Microstructure And Mechanical Properties Of 316L Hybrid Manufacturing Parts Based On SLM Process

Selective laser melting(SLM)is a kind of additive manufacturing technology that can accurately manufacture high-performance metal parts with complex structures,and has received widespread attention.However,it uses small spots to manufacture parts layer by layer,resulting in low processing efficiency and high cost.For parts with a local fine structure,the existing overall selective laser melting manufacturing technology is difficult to balance high efficiency and low cost,which restricts its popularization and application.In contrast,the traditional manufacturing process can realize the mass production of simple structural parts with high efficiency.Therefore,the hybrid manufacturing technology that combines the SLM process and the traditional manufacturing process takes into account the requirements for complex structures and the control of time and cost Based on this,this subject carries out research:hybrid manufacturing technology based on SLM process.The main research contents are as follows:(1)The design and processing plan of hybrid manufacturing samples was formulated.Designed and processed hybrid tensile specimens,SLM tensile specimens and substrate tensile specimens with different placement methods.The microstructures of the SLM zone,the substrate zone and the interface bonding zone of the hybrid manufacturing sample were mainly studied,and the tensile properties of hybrid manufacturing specimens were compared with substrate specimens and SLM specimens.In addition,the microhardness distribution of the hybrid manufacturing specimen along the manufacturing direction was tested.There was no crack at the interface between the substrate zone and the SLM zone of the hybrid manufacturing samples.After the vertical hybrid tensile specimens were broken,the fractures were located on the substrate,indicating that the strength of the bonding surface was better than the strength of the substrate and can meet the requirements of use.The tensile strength and elongation of the horizontal hybrid tensile specimens were between the SLM specimens and the substrate specimens.(2)The heat treatment process was formulated to characterize and analyze the microstructure and mechanical properties of the hybrid manufacturing samples after heat treatment.The microstructure and mechanical properties of the hybrid manufacturing samples before and after heat treatment were compared and studied.After heat treatment,the grain size of the SLM zone and the substrate zone increased significantly.Under the action of heat and internal stress,the grain growth of the hybrid manufacturing sample caused the interface to disappear and a transition zone appeared between the two different forms of grains.The transition zone was mainly composed of equiaxed austenite grains,its grain size was significantly smaller than the substrate zone.The tensile strength of the hybrid manufacturing specimens in the vertical direction was reduced,and the elongation was improved;the tensile properties of the hybrid tensile specimens in the horizontal direction had the same changing trend.(3)The commercial finite element analysis software ANSYS(APDL)was used to establish a single-layer multi-track three-dimensional transient numerical model of hybrid fabricated 316L stainless steel.Based on the finite element model of hybrid manufacturing 316L stainless steel,the distribution and evolution of temperature field and stress field during hybrid manufacturing were studied,and the influence of different preheating temperatures and scanning strategies on the thermal behavior,stress evolution and residual stress distribution of the molten pool were analyzed.As the preheating temperature increased,the maximum cooling rate and the temperature gradient of the molten pool boundary gradually decreased,and at the same time,the residual stress also decreased.For partition scanning,the partition size largely determined the heat accumulation during SLM processing,which in turn affected the cooling rate and temperature gradient.Partition scanning reduced the residual stress of the part to a certain extent,and as the partition increased,the scanning length was shortened,and the residual stress was reduced more significantly.