Mechanical Properties And Biocompatibility Of 316L Stainless Steel Porous Structure Formed By Selective Laser Melting

The application of porous materials in artificial implants has always been the focus of research in related fields.In the field of medical implants,porous metal materials have been widely used because of their good plasticity and strength to solve the low biocompatibility problem caused by the"stress shielding"effect.Due to the very complex irregularity of human bone tissue,the porous metal structure of regular unit has been difficult to meet the requirements of controllable mechanical properties and bionic structure.In this paper,based on the above reasons,an irregular porous structure controlled by the probability sphere model was designed based on Voronoi algorithm,and the porous structure was prepared by selective laser melting technology,and the mechanical properties and biocompatibility of the porous structure were tested.The research contents of this paper are as follows:(1)Design of irregular porous structure.Through the probability sphere model,the random number of space is controlled,and the Voronoi-Tessellation principle is used to divide the spatial region constrained by random points into grids.Based on the control of random number,the irregularity of porous structure is adjusted.In this paper,the irregular porous structure is modeled by the parametric modeling software Rhinoceros,and the parameters of the irregular porous structure are characterized,which provides a new idea for the design of irregular porous structure.(2)Preparation of porous structure.Due to the complex geometrical properties of porous structures,Selective Laser Melting(SLM)technology can be used to shape the porous structures.In order to prepare porous metal implants with good mechanical properties and microstructure,the effects of technological parameters on the density,porosity difference and roughness of 316L forming parts were studied.The results show that the density,porosity difference and surface roughness are 99.25%,0.60%and 4.39μm for the samples prepared by the optimal process parameters.When the energy density is 109.65～145.83J/mm~3,the melting state of powder is the best.(3)Analysis of mechanical properties of porous structures.The apparent elastic modulus and compressive strength of porous structures were measured by quasi-static compression tests,and a multivariate nonlinear prediction model of porosity,elastic modulus and compressive strength was established.The results show that the optimal structural parameters of irregular porous structure are as follows:strut diameter0.4mm,irregularity 0.2,seed points 294 and unit distance 1.72mm.The elastic modulus and compressive strength of the porous structure designed in this paper are close to the natural bone tissue of human body,and meet the application requirements of medical porous structure.(4)Study on biocompatibility of porous structures.Two series of porous structures,porosity and irregularity,were designed and prepared by using the optimized technology and the established multivariate nonlinear prediction model,and the cells were cultured in vitro.The results showed that the porous structure of316L stainless steel prepared by SLM showed a good growth condition in the process of cell culture in vitro.High porosity and high irregularity would promote the proliferation and differentiation of cells.