Study On The Mechanism Of Laser 3D-Printing Of Simulated Lunar Soil

Lunar soil is a rich resource which can be seen everywhere on the surface of the moon.In-situ development and effective utilization of lunar soil are of great significance to reduce the dependence and consumption of earth resources in the process of lunar development.Use of lunar soil cannot be separated from the development and research of its forming technology.Laser 3D printing is an advanced industrial technology that can directly convert digital models into solid parts,artworks and other products through layer-by-layer additive manufacturing using laser heat source.It can realize the manufacturing of high melting point materials with complex shaped,so it may become one of the effective ways of lunar soil forming in the future.However,there are very few of real lunar soils on the earth,which cannot meet the needs of scientific research and engineering applications.Therefore,many kinds of simulated lunar soils have been developed and applied to scientific research.There may be some differences between the simulated lunar soil and the real lunar soil due to the difference of environment between the lunar surface and the surface,and that of geographical environment among each part of the lunar surface.Therefore,the study on the physicochemical evolution and sintering characteristics of each component during the process of forming the simulated lunar soil is helpful to improve the process and forming equipment,and lay a solid foundation for the formation of real lunar soil in high vacuum environment.Based on this,in this paper,low-titanium basalt simulated lunar soil CLRS-1 and high-titanium basalt simulated lunar soil CLRS-2 were sintered by conventional tubular furnace and laser under the atmospheric and vacuum conditions,and the composition evolution and forming characteristics of two basalt simulated lunar soils during sintering process were studied.The main research works and results are summarized as follows1)Conventional sintering of CLRS-1 and CLRS-2 lunar simulated soils was carried out under vacuum and air respectively.The sintering temperatures were set to 600,700,800,900,1000,1050,1100 and 1150℃,respectively.The weight loss and density of sintered samples at different sintering temperatures were measured,and the effect of vacuum atmosphere on sintering process was analysed.Macro pores were found in both two sintered simulated lunar soils samples when sintered in vacuum at high temperature(>1100℃).The micro-morphology and composition of samples sintered at different temperatures were studied by means of SEM,EDS,XRD and XRF.The reasons for pore formation under vacuum conditions were analysed,and the composition evolution of two representative simulated lunar soils during vacuum sintering were summarized.Meanwhile,the thermal conductivity of CLRS-1 porous samples was measured at 25℃(room temperature),123℃(maximum temperature of the lunar surface)and 600℃.2)Laser sintering of CLRS-1 and CLRS-2 was carried out in air.The effects of scanning speed,laser power and laser working distance on the forming process were studied.3)The finite element numerical simulation method was used to study the difference of temperature distribution in powder bed between air and vacuum condition.The influence of temperature distribution on the forming process was also studied.The effects of evaporation of lunar soil components and bad heat transfer of powder bed on sample formation during laser sintering under high vacuum were analyzed.