Simulation And Experimental Study On The Absorption Behavior Of Tungsten Alloy Based On Selective Laser Melting

In this paper,based on the close combination of Fred optical simulation and experimental research,the laser absorption behavior during selective laser melting(SLM)based on pure tungsten and tungsten heavy alloy powder particles was studied.The changes of the scanning track,surface roughness and grain orientation during SLM with different powder particle sizes were discussed.The influence of scanning speed and laser power on densification and microstructure and mechanical properties were further revealed.Based on the simulation of the pure tungsten regular model,the effect of different particle sizes on the absorption behavior of the powders was studied.When the particle diameter was 5?m,the absorptivity of the pure tungsten powder layers reached the maximum value of 0.6030.The distribution of laser irradiance on the particle surface was sensitive to particle size,azimuthal angle,and the position of the powder particles on the substrate.The maximum irradiance in the powder layers decreased from 1.117×10^–3 to 0.85×10^–3 W·?m^–2 and the contour of the irradiance distribution in the center of the irradiated area gradually contracted when the particle size increased from 5 to 45?m.Then,the random model was obtained by the sequence addition method.In the random model,the laser absorptivity and the number of laser rays after the interaction increased significantly.Laser irradiance was completely absorbed by surface powders,and the absorptivity can reach 0.705 when the particle size was 5-25?m.Through the experiment of SLM processed pure tungsten,the influence of particle size on microstructure and mechanical properties has been clarified.Moreover,the absorption behavior mechanism of pure tungsten was verified.The crystal growth mechanism of pure tungsten during SLM was clarified,and cracks can be effectively controlled.The study found that the laser scanning tracks were more continuous and regular due to the higher absorptivity of small particle size powders.As the particle size increased,the surface roughness of multiple tracks increased.When the particle size of the powder was small,the cracks of the pure tungsten decreased significantly and the grain orientation was changed.At this time,the content of LAGBs(Low Angle Grain Boundaries)was significantly larger.The dislocation density and local stress were lower,and the preferred orientation was obvious.Finally,a considerably high hardness of 439 HV,a superior compressive strength of 935MPa were obtained.Through the simulation of the random model of W-Ni-Fe composite powders,the influence of the addition of nickel and iron on the absorption behavior was clarified.The influence of nickel/iron particle size on the laser absorptivity and absorption irradiance of W-Ni-Fe were further studied.The powder size was optimized based on the simulation results,and parameter optimization experiments of SLM were carried out.The absorptivity was increased to 0.72 by the addition of nickel and iron.The smaller the particle size of nickel and iron,the higher the absorptivity of the W-Ni-Fe composite powders.The laser irradiance increased to 1.28×10^–3 W·?m^-2.The compressive strength and microhardness both increased and then decreased with the increase of the laser energy input.The compressive strength reached 2638 MPa and the maximum microhardness reached 531.975 HV.