Experimental Study On Quality Control Of SLM Forming 316L Stainless Steel Products

Laser selective melting(SLM)is the core part of laser augmentation manufacturing.Its forming component has high surface accuracy and good performance.It has a very broad application prospect in the production of additional materials.In this paper,the quality of 316 L products produced by selective laser melting is controlled,the optimized process parameters are determined,and the effects of different laser linear energy density on the properties of forming components are studied.At the same laser energy density,the effects of different laser power and scanning speed on the properties of the formed components and the fracture morphology after heat treatment were analyzed.Specific research contents are as follows:First of all,by investigating relevant literature,it is determined that the quality of regulated products is a method of adjusting process parameters.Then,before preparing the sample,a small amount of 316 L stainless steel powder was selected for observation and analysis.To determine the particle size of the powder,the surface shape of the powder,and the element content,the range of process parameters of the forming is initially determined to prepare a sample.The effects of laser line energy density on the surface morphology of the formed members were studied.The effects of different laser power and scanning speed on the microstructure of the formed members were also studied under the same laser line energy density.After analysis,it is found that there are some large holes on the surface of the specimens,but small holes appear less in the components when other parameters remain unchanged and laser linear energy density is high.When the laser linear energy density is 0.18J/mm,the surface porosity of the formed component is smaller.At the same laser linear energy density,when the laser power is 180 W and the scanning speed is 1000mm/s,the surface of the formed component has fewer voids and the forming quality is the best.When the laser power and scanning speed are small,the surface quality of the formed parts is the worst.In a certain range,with the increase of laser power and scanning speed,the surface quality of the formed parts becomes better and better.When the quality reaches the best,it gradually decreases.Secondly,the relative density and mechanical properties of the members under different laser line energy densities are studied.When the laser linear energy density is 0.18J/mm,the density of the formed component is the best,reaching 97.76%.At the same time,the surface hardness of the formed component is the best,and the tensile strength can reach 790 MPa.Continuously increasing the laser energy density,the density of the component decreases,and the surface hardness and tensile strength also decrease.However,when the laser linear energy density is low,the performance of the formed metal components is poor.At the same time,the effects of different laser power and scanning speed on the density and mechanical properties of the formed parts under the same laser linear energy density were also studied.The experiment shows that different laser power and scanning speed have different effects on the performance of the parts under the same laser linear energy density.When the laser power and the corresponding scanning speed are small,the quality of the formed parts is low.When the laser power reaches 180 W and the scanning speed is 1000mm/s,the quality of the formed parts is the best,the surface hardness and tensile strength are also the best,and the tensile strength can reach 790 MPa.When the laser power exceeds 180 W,the corresponding scanning speed increases.However,the quality of its forming has not been improved,but gradually decreased.Finally,the optimized process parameters are used to form the test piece.It was then heat treated at 1050 C for 30 minutes.The specimens were cooled to room temperature by water cooling and air cooling,respectively.The mechanical properties and fracture morphology of the specimens were studied.The tensile strength and elongation of the formed components are better than those obtained by water cooling under air cooling.However,after heat treatment,the tensile strength of the components decreases and the elongation increases correspondingly.The fracture mode of SLM forming parts is ductile fracture.After heat treatment,the specimens also show ductile fracture.The influence of laser linear energy density on the quality of metal forming is obtained by optimizing the process parameters of laser forming,and the influence of different laser power and scanning speed on the quality of metal forming under the same laser linear energy density is obtained.It provides a reference basis for determining suitable forming parameters of 316 L stainless steel by laser selective melting equipment.At the same time,it can provide a basis for selecting suitable laser for laser selective melting equipment.After heat treatment on the surface of the formed components,the tensile strength and surface hardness of the formed specimens are obviously reduced,and the elongation is increased.The fracture mode of the formed parts and the heat treated specimens are ductile fracture.