激光选区熔化316L不锈钢成形工艺优化及力学性能研究OA

High residual stress,insufficient relative density and large dispersion of mechanical properties are commonly found in the selective laser melting(SLM)forming of 316L stainless steel.Aiming at the collaborative optimization of process,microstructure and properties,the influences of laser power(P),scanning speed(v),powder layer thickness(h)and their interactions on forming quality are systematically explored based on multi-factor orthogonal tests and response surface methodology(RSM).Firstly,an L9(34)orthogonal test is designed,and the data of relative density,residual stress,hardness and tensile properties are collected.Subsequently,a relative density prediction model is established by RSM,and the evolution mechanism of microstructure is revealed via multi-scale characterization of SEM,EBSD and TEM.The optimal process window is further verified by simulation.The average relative error between predicted and measured values is only 0.012,which proves the correctness and reliability of the model.The results show that when P=300 W,v=1 000 mm/s and h=30 µm,the relative density of samples reaches 99.2％,with tensile strength of 650 MPa,yield strength of 520 MPa,elongation of 35％and Vickers hardness of HV245.Its comprehensive properties are obviously better than those specified in ASTM A276 forging standard.The microstructure presents fine honeycomb cellular structures with size of 1～3 µm.High dislocation density(1.2×101 4 m-2)and nano-Cr2O3 dispersed precipitates jointly provide a strengthening increment of about 340 MPa.This study provides theoretical basis,process window and post-processing schemes for high-performance additive manufacturing of complex thin-walled precision components such as turbine blades and fuel nozzles in aerospace field.