Laser Powder Bed Fusion and Hot Forging of 316L Stainless Steel: A Hybrid Additive Manufacturing Approach for Enhanced Performance.

Forging plays a crucial role in various industries, including aerospace, automotive, oil and gas, and defense. We investigated the effect of post-processing forging on microstructural and mechanical properties of 316L stainless steel forging preforms fabricated by laser powder bed fusion. The as-built samples were subjected to hot forging in order to refine the microstructure and enhance mechanical performance. Detailed characterization was performed using Electron Backscatter Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Tensile testing, and Hardness Testing. Substantial grain refinement (up to 97%) was observed, in addition to a reduction in porosity. The forging process effectively transformed the columnar grain morphology into equiaxed grains, increased yield and ultimate tensile strengths of 560 MPa and 740 MPa, representing 27% and 32% improvements, respectively, with a corresponding decrease in elongation to 32% from 47%. The horizontally built samples achieved the highest yield strength of 605 MPa but slightly lower UTS 710 MPa, representing 32% and 5% increment and decrease in ductility to 28% from 37.5%. These trends reflect the combined effects of work hardening and grain refinement, which enhance strength at the expense of ductility.