Research On Path Planning And Process Of 316 Stainless Steel Multi-Layer And Multi-Bead Parts By Laser Induced Arc Additive Manufacturing

As a new type of rapid net forming technology,additive manufacturing has the unique advantages of energy saving,green environmental protection,high efficiency and low cost.China has incorporated it into one of the core technologies of green intelligent manufacturing.At present,many countries in the world have invested a lot of resources in this technology,aiming to seize the commanding point of advanced manufacturing industry.Additive manufacturing has become the key technology in the industrial 4.0 era and is the engine driving the development of the next generation industrial revolution.As a manufacturing power,China must grasp this technology to make manufacturing industry revitalize and lead China's industry to the top of the world.Among the metal additive manufacturing filler materials,austenitic stainless steel is widely used.316 stainless steel is used in aerospace,automobile ship,biomedical and other fields due to its good weldability and excellent mechanical properties.At present,the research on additive manufacturing of 316 austenitic stainless steel mainly focuses on single heat source,single bead and multi-layer thin-walled parts.However,single heat source has manufacturing limitations,and it is impossible to manufacture thin-walled parts only in industry.Therefore,it is urgent to study additive manufacturing technology of multi-layer and multi-bead thick wall parts and hybrid heat source.In this paper,316 stainless steel multi-layer and multi-bead thick wall parts were made by TIG arc and laser induced TIG arc.The research contents and conclusions were as follows:For the single TIG arc additive manufacturing,the surface macroforming,microstructure,element distribution and properties of the three paths of the parts were studied,which were parallel reciprocating,cross shaped and insert stacking.The results showed that the surface of the parts with parallel reciprocating and cross shaped path was more flat.The microstructure of the middle area of the part was obviously different,and the dendrites of parallel reciprocating parts were thick and developed,and the growth direction was consistent.The dendrite growth direction of cross shaped part was many,the dendrites were disordered and the transition area between layers was large.The secondary dendrites of the insert stacking parts were not developed and the microstructure was fine.The Vickers hardness of the part decreased first and then increased from the bottom to the top.The longitudinal tensile strength of the parallel reciprocating part was the highest,the transverse tensile strength of the insert stacking part was the highest,and the mechanical properties of the cross shaped part showed isotropy.The Ni and Cr elements at the bottom of the part were distributed at the grain boundary of the cellular austenite.The Ni elements in the middle and top of the part were mainly concentrated in austenite,while Cr was mainly concentrated in ferrite.For the laser induced TIG arc additive manufacturing,the same experiment method and testing method as the single TIG arc additive manufacturing were used to analyze the macro forming,microstructure,element distribution,grain orientation and mechanical properties of the part.The experimental results were compared with the results of single TIG arc additive manufacturing.The changes of arc shape,heat input and microstructure and properties of the part after laser addition were discussed.The results showed that the arc had shrinkage effect,the stability and efficiency of the additive manufacturing increased and the heat input decreased.The oxidation degree of the part was reduced,and the surface of the insert stacking part was more flat.There was no ferrite formation at the bottom of each part,and Ni and Cr were mainly distributed along the grain boundary.The Ni elements in the middle and top were concentrated at ? austenite,Cr elements were concentrated at ? ferrite,and the deflection of the top dendrite weakened or even disappeared.The transition zone of cross shaped part was narrower,and the microstructure of the three paths of the part was smaller than that of the single TIG arc part,and the grain boundary was mainly distributed at a small angle.The microhardness and tensile properties of the parts were improved to different degrees after adding laser.