Mechanical Properties And High Temperature Oxidation Behavior Of Selective Laser Melting IN625 After Laser Shock

Selective laser melting(SLM),as an additive manufacturing technology for processing metal materials,has unique technical advantages in forming high-performance metal parts with complex structure.However,there are many defects in SLM parts,such as surface cracks,poor metallurgical bonding,excessive residual stress and so on.In this paper,the effects of laser energy density on the surface quality,internal defects,microstructure,mechanical properties and high temperature oxidation behaviors of Inconel 625(IN625)alloy formed by SLM were studied;The influence mechanism of laser shock peening on microstructure,mechanical properties and high temperature oxidation behaviors of IN625 alloy was further studied.The main research contents and results are as follows:Basic theoretical research on SLM process and laser shock of IN625 alloy:The forming mechanism of SLM and the mechanism of laser shock strengthening are analyzed theoretically;The key influencing factors of SLM forming process were explored;The theoretical basis of laser shock strengthening is clarified.The results show that controlling the laser energy density is an effective way to affect the microstructure and comprehensive properties of SLM samples.The mechanical properties of SLM samples can be effectively strengthened by laser shock processing.Forming mechanism of SLMed IN625:The effects of laser energy density on the surface morphology,internal defects and microstructure of IN625 alloy were systematically studied;The changes of mechanical properties of IN625 samples under different laser energy density were clarified;The relationship among laser energy density,microstructure and properties is established;The forming mechanism of IN625alloy prepared by SLM was revealed.The results show that the laser energy density is an important parameter affecting the surface morphology,internal defects and microstructure of IN625 samples.At high laser energy density(167 J/mm³),the IN625sample with high surface quality and less internal defects can be prepared by SLM.At high energy density,the mechanical properties of IN625 are slightly higher,which can be attributed to the combined effect of higher density,lower residual tensile stress and larger grain size.Micro response and strengthening mechanism of SLMed IN625:The effect mechanism of laser shock on surface morphology and microstructure of SLM formed IN625 alloy was systematically studied;The influence of laser shock on the mechanical properties of IN625 was analyzed;The mapping relationship among laser shock processing,microstructure and mechanical properties was established;The strengthening mechanism of mechanical properties of IN625 alloy formed by SLM was revealed.The results show that the laser shock causes round pits on the surface of IN625sample,which leads to grain refinement and dislocation proliferation on the surface of the sample,and introduces residual compressive stress on the sample surface.After laser shock,the mechanical properties of the samples are improved significantly,which can be attributed to the comprehensive effects of grain refinement,dislocation growth and residual compressive stress.High temperature oxidation behavior of SLMed IN625:the effects of laser energy density and laser shock process on high temperature oxidation behavior of SLM formed IN625 alloy were systematically studied;The high temperature oxidation mechanism of IN625 alloy formed by SLM was clarified;The relationship between laser energy density,laser shock and high temperature oxidation performance was established;The enhancement mechanism of laser energy density and laser shock on high temperature oxidation performance was investigated.The results show that the high temperature oxidation process of SLM forming IN625 alloy can be divided into two stages,the first stage is chemical adsorption,and the second stage is atomic diffusion.At high laser energy density(167 J/mm³),dense Cr₂O₃ oxide film was formed in the high temperature oxidation process,and it has good high temperature oxidation performance.After laser shock,the high temperature oxidation properties of the samples are further strengthened by the combination of defect healing,grain refinement,dislocation proliferation and surface residual compressive stress.