Analysing the Impact of Severe Shot Peening on the Fatigue Strength of Wire Arc Additively Manufactured Carbon Steel

Abstract

The study investigates the impact of severe shot peening on the fatigue strength of wire arc additively manufactured carbon steel. Initial characterization revealed a material with prominent equiaxed grains and large grain sizes. However, the application of SSP induced a considerable reduction in grain size, particularly on the surface, consequently enhancing the surface's strength and hardness, yet leading to an inhomogeneous structure within the WAAM CS SSP part. Hardness measurements demonstrated a substantial impact on surface hardness, reaching a depth of approximately 0.4 mm, with a 64% increase observed due to SSP, elevating it from an average of 165 HV to a maximum of 270 HV near the surface. Tensile tests on WAAM CS and WAAM CS SSP displayed notable improvements in mechanical properties following SSP treatment. Yield strength increased by approximately 5%, and ultimate tensile strength rose by 2.5%, resulting in a peak tensile strength of 513 MPa. However, this enhancement was accompanied by reduced ductility, evidenced by decreased elongation from 44% in WAAM CS to 35% in WAAM CS SSP. Bending fatigue tests highlighted a significant enhancement in fatigue resistance due to SSP treatment. The fatigue limit increased by 21% from 190 MPa for WAAM CS to 230 MPa for WAAM CS SSP, indicating improved resistance in both low-cycle and high-cycle fatigue regimes. This enhancement in fatigue resistance is attributed to the heightened mechanical strength post-SSP treatment, suggesting a trade-off between increased strength and reduced ductility. The results demonstrate that SSP significantly enhances surface attributes, strength, and fatigue resistance of WAAM CS. This advancement bears implications for engineering applications where enhanced mechanical properties and fatigue resistance are vital, despite the induced trade-offs in material characteristics.