Effect of Shot Peening and Its Parameters on Surface Quality, Microstructure and Hardness of 316L Stainless Steel Fabricated by Material Extrusion Additive Manufacturing

The specimen was prepared using the material extrusion additive manufacturing (MEX/M) process. Shot peening was performed using 304 stainless steel media with two different shot sizes (60 μm and 200 μm) at the pressures of 2, 4 and 6 bar. Surface quality was assessed through surface roughness measurements. The results indicated improved surface quality under all processing conditions, with larger media being more effective. Furthermore, shot peening effectively eliminated the Al2O3 particles on the surface. Phase analysis was conducted using X-ray diffraction, while microstructural analysis was performed using optical microscopy and scanning electron microscopy. The results showed that martensite formation was observed near the surface and surface microcracks under all peening conditions after shot peening. Mechanical properties, specifically microhardness at a depth of 10 μm, revealed that the larger media and higher peening pressure significantly enhanced surface hardness.