Model Analysis And Experimental Study Of Porous Scaffolds Formed By Selective Laser Cladding

With the aging of population in modern China,more and more bone diseases come into people’s sight.In order to repair or replace the damaged human bones,and better solve the problems of elastic modulus and mechanical properties between artificial medical implants and natural human bones,medical metal porous stent implants are often used in modern medical surgery.Choosing the appropriate porosity and pore size of the stent can not only effectively replace and match the bone of the diseased part of the patient,It can not only avoid the problems of "stress shielding" and "stress concentration",but also accelerate the enrichment and growth of cells by virtue of the rough scaffold surface and porous structure of the channel,which is conducive to the transmission of nutrients for cell metabolism.The traditional machining process is difficult to meet the accuracy requirements of complex porous structure,different porosity and pore size.However,by using computer-aided design software to build the model and selective laser melting(SLM)technology,medical porous scaffolds with precise size and complex structure can be prepared,It can be customized according to patients of different ages and different diseased parts,so as to repair and replace the diseased bone more efficiently.In this thesis,the models of porous scaffolds with different structures are built by UG and C4D(Cinema 4D)modeling software.According to the mechanical properties of human bones,the pore size and pore size close to their properties are designed.The 316L stainless steel powder is 3D printed,and the porous scaffolds with different structures and porosity are prepared.The mechanical properties of porous scaffolds with similar porosity and self-growing porous scaffolds with different porosity were studied by metallographic observation,solid solution and annealing heat treatment,hardness test,compression test,scanning electron microscope analysis and cell driven analysis.By establishing the models of traditional regular square,circular and self growing porous scaffolds with similar porosity,316L stainless steel powder was prepared by selective laser melting(SLM)technology,and then the scaffolds were treated by solid solution and annealing heat treatment.Finally,the mechanical properties of three kinds of porous scaffolds before and after heat treatment were analyzed by compression test,It is found that the mechanical properties of self-growing porous scaffolds before and after heat treatment are better than those of traditional porous scaffolds with regular shape.For self growing porous scaffolds,the porosity of scaffolds increases and the degree of pore distribution decreases with the increase of the scale size.When the porosity and the degree of pore distribution of scaffolds are in an average degree,the mechanical properties of self growing porous scaffolds are better than those of other scale sizes.The precision of the porous scaffolds prepared by selective laser meltingis high,but there are some defects in the porous scaffolds,such as uneven powder melting,cracks and pores,which increase the surface roughness of the scaffolds to a certain extent,and are more conducive to cell attachment and growth.The 316L stainless steel powder was melted by high-energy laser and then cooled rapidly in air.Under the observation of metallographic microscope,the surface structure of porous scaffold was mostly composed of regular parallel arrangement of columnar dendrites,and the meltingtracks were 60 ° included angle;According to the hardness test results,the surface hardness deviation of porous scaffolds is small,which indicates that the surface microstructure of porous scaffolds prepared by high-energy laser melting 316L powder is uniform.After solution and annealing heat treatment,the range of surface hardness value decreases,and the surface microstructure becomes more uniform.At the same porosity of 43%,the loading capacity of 316L self-growing porous scaffolds prepared by SLM technology is higher than that of traditional regular round and square porous scaffolds.At the same time,the surface of scaffolds contains more micro scale pores,which has larger cell curvature driving effect,and is more conducive to cell enrichment and new tissue expansion.