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

Area of Science:

• Materials Science
• Metallurgy
• Additive Manufacturing

Background:

• Forging is vital for aerospace, automotive, and defense industries.
• Laser powder bed fusion (LPBF) is an additive manufacturing technique used for creating metal components.
• 316L stainless steel is a widely used material in demanding applications.

Purpose of the Study:

• To investigate the impact of post-processing forging on the microstructure and mechanical properties of LPBF-fabricated 316L stainless steel.
• To determine the effectiveness of hot forging in refining grain structure and improving material performance.
• To compare the properties of forged samples with as-built LPBF samples.

Main Methods:

• Laser powder bed fusion (LPBF) was used to fabricate 316L stainless steel preforms.
• Hot forging was applied as a post-processing technique.
• Characterization involved Electron Backscatter Diffraction (EBSD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), tensile testing, and hardness testing.

Main Results:

• Substantial grain refinement (up to 97%) and reduced porosity were observed after forging.
• The forging process transformed columnar grains into equiaxed grains.
• Yield strength increased by 27% (to 560 MPa) and ultimate tensile strength by 32% (to 740 MPa), while elongation decreased from 47% to 32%.

Conclusions:

• Post-processing forging effectively refines the microstructure of LPBF 316L stainless steel.
• Forging significantly enhances yield and ultimate tensile strength, albeit with a reduction in ductility.
• The study demonstrates the potential of combining additive manufacturing with forging for improved material properties.