3D Numerical Modeling Of Thermodynamic Characteristics Of Surface Powder Melt Pool In Selective Laser Melting

Additive Manufacturing(or so-called 3D printing)technology is one of the most popular research directions and achievements in the world in recent years,and Selective Laser Melting(SLM)is now a commonly used process.However,high heating and cooling rates locate around the laser spot in a small region,leading to phase transformation under a high thermal gradient difficult to be tailored by experimental studies and there are defects produced such as cracks,so increased efforts are needed to produce parts with desired geometrical and mechanical properties.In order to optimize process parameters,numerical models are currently proposed for AM processes.A particle scale finite element numerical model is presented for Selective Laser Melting(SLM)of Inconel 718 alloy.In the numerical model,the non-linear thermal analysis and the following hydrodynamic simulation are performed to study the particle melting and melt pool evolution,in which the level set method is used to track the motion of an interface between gas and metal material domains.To obtain reasonable temperature distribution and melt pool dimension,both volumetric and surficial heat source models are proposed.The influences of different process parameters on temperature distribution and on melt pool profiles are discussed for both fixed and moving heat source.By this simulation model,it's possible to observe the particles melt and collapse under the imposed heat source,in which the dynamic temperature distribution and fluid flow velocity are possible to captured,and to observe the porosities due to the insufficient melting.For the volumetric heat source model,in case of the fixed laser beam,it is found that 200 W laser power and big size particle produce fewer pores;in case of mobile laser beam,the porosities are found again.By analysis of laser scan velocity and laser power,the sizes of melt pool are greatly influence by the ratio of laser power and laser scan velocity(linear energy).Simulation tests by the surficial heat source model are also performed.For the fixed laser beam,few pores are found compared with that of volumetric heat source model.For the mobile laser beam,more reasonable melt pool sizes are obtained and comparable with those from experiments.This developed model could predict the melt pool width within 1.7% error.The proposed numerical model is able to optimize process parameters and reduce experimental costs.