Laser-Based Additive Manufacturing and Mechanical Surface Post-Processing: Comparison of Barrel Finishing, Shot and Ultrasonic Peening for Corrosion Resistance Improvement of Superalloy

Nickel-based alloy test parts were manufactured using an industrial laser 3D printing system. The corrosion behavior of the laser powder bed fused (LPBF) Inconel 718 alloy parts are analyzed in as-built and mechanical surface post-processed conditions, i.e. after barrel finishing, shot peening, ultrasonic shot peening, and multi-pin ultrasonic impact treatment. The microstructural features are analyzed using the X-Ray diffraction (XRD) analysis and scanning electron microscopy (SEM) / energy dispersive spectroscopy (EDS) methods. The open circuit potential and linear/cyclic polarization were registered in a 3.5 wt.% NaCl solution. The surface roughness diminishment, defects elimination, residual pores’ closure, as well as the residual stress and structure-phase state changes were under special attention. The polarization resistance, corrosion current density, corrosion rate, pitting initiation rate, anodic dissolution, ability for repassivation, and crevice corrosion resistance were assessed and compared.