Impact of pore defects on laser additive manufacturing of Inconel 718 alloy based on a novel finite element model: Thermal and stress evaluation

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In this study, for further understanding the complex stress distribution within the cladding layer, the pore defect distribution model and three-dimensional transient thermo-elastic–plastic model with sequential thermal-force coupling are established to realize the dynamic simulation of the temperature and stress fields in laser additive manufacturing of Inconel 718 alloy with different pore defects, and to investigate and analyze the effects of pore defects on the temperature and stress distribution within the clad layer by a multi-path method. The increase in porosity leads to a decrease in the temperature and temperature gradient, and an increase in cooling rate of the melt pool during solidification. The tensile limit of the cladding parts with porosity defects is 524.18 MPa, which is 41.91% lower than the theoretical value; and the stress distribution is more uneven, where the residual stress at the defects increases. By constructing a model considering the porosity defects, the stress on the surface of the cladding part is close to the actual measuring stress distribution of 186–272 MPa using X-ray diffraction, which effectively avoids the data singularity with the maximum error reduced from 21% to 16%. This study further explains the phenomenon of cracking within the cladding layer despite stress well below the theoretical tensile limit in previous simulation, and can provide reasonable process optimization guidance for the defect suppression in additive manufacturing.