Numerical Simulation And Experimental Verification Of The Flow Characteristics Of The Ceramic Laser Selective Melting Pool

Ceramic materials are popular for their high melting point,high hardness,corrosion resistance,oxidation resistance,biocompatibility,etc.However,it is difficult to process complex or high-precision ceramic parts with traditional processing techniques.Selective laser melting(SLM)technology can directly form high-precision or complex parts,and is a potential manufacturing technology for processing ceramic parts.At present,ceramic SLM is still in its infancy,and many phenomena need to be explained.In this paper,the computational fluid dynamics was used to simulate the alumina SLM process,and the effects of key process parameters on the temperature field,flow field and surface morphology of the parts were studied and verified by experiments.Main work of the paper is as follows:(1)Combined with characteristics of ceramic SLM,the physical phenomena such as heat conduction,heat convection,Marangoni convection in the molten pool and latent heat are considered.The thermal property parameters varying with temperature of alumina were set and the three dimensional heat-flow coupling model was established.The moving Gaussian volumetric heat source was loaded and transient analysis and calculation was carried out.The thermal field and flow field calculation results of multi-channel forming of alumina SLM were obtained.(2)The effects of laser power,scanning speed and preheating temperature on temperature field distribution,melting degree,liquid life,temperature changing rate and flow intensity were studied.(3)To study the stripy and finger-shaped micro-morphology on the surface of ceramic SLM parts,combining with the convection theory of Bénard-Marangoni of fluid mechanics,the temperature field and flow field results were used to clarify the formation mechanism of solidification microstructure on the surface of alumina SLM forming parts.Simulations were performed by changing the variables like laser power,scanning speed,and preheating temperature to predict the influence of processing parameters on the solidification structure.(4)The alumina SLM experiment was carried out,and the simulation results were compared with the experimental results to verify the simulation results.According to the conclusion,suggestions for avoiding solidification streaks on the surface of formed alumina SLM parts are given.