Process And Properties Of Ni-based 718 Alloy Formed By Selective Laser Melting

Selective Laser Melting technology based on the principle of calculus,The single-layer powder is selectively melted by using high-energy laser beam according to the contour data,and three-dimensional solid parts are manufactured by layering,layer-by-layer melting and solidification.The technology is not subject to the complexity of the parts with short processing cycle,high material utilization,high qualification rate,personalized customization and so on.Due to the particularity of selective laser melting technology,it has high requirements on process control,material properties,process reliability and laser beam stability.It is liable to affect the quality of parts due to improper forming process.Domestic research on Inconel 718 alloy is relatively less.Therefore,in this work a study on process,structure and properties on the relative density,microstructure mechanical properties of Inconel 718 alloy,which provides a theoretical basis for the figuration manufacture of nickel-based alloy formed by selective laser melting.In this paper,the influence of process parameters on relative density,microstructure,mechanical properties and phase distribution of Inconel 718 Alloy is investigated through selective laser melting forming process experiment.The study found that the scanning speed and laser power are the main factors that influence the formability.Based on the process test,the optimum process parameters of the alloy is achieved: laser power is 315 W,scanning speed is 1050 mm/s,scanning interval is 0.09 mm,layer thickness is 0.04 mm.Under the optimum process parameters,we can obtain less porosity,crack defects and the relative density of 98.94 %,tensile strength and yield strength are both exceed the traditional casting process and closed to the forging + annealing process performance,The elongation is 3 times that of traditional castings.The microstructure of Inconel 718 samples is uniform and dense,and the columnar crystal with directional solidification are uniformly arranged.Its heat dissipation lead to the difference of the microstructure morphology.The columnar crystals with directional solidification can be obtained by controlling the process parameters in the stratification direction.The tensile properties are related to the heat-affected zone between the settled layers.And the hardness of the samples increased with the refinement and densification of the microstructure.The defects and mechanism,such as spheroidizing,crack,spatter and porosity,existing in the selective laser melting technology are analyzed.The defects can be effectively suppressed by optimizing the process parameters.High-density and high-performance formed parts can be obtained by selecting a substrate of good wettability with alloy material and higher expansion coefficient than it,drying materials powder and improving the thermal cracking resistance of materials.