Nonlinear Ultrasonic Characterization of Processing Defects in Wire Arc Additive Manufacturing 316L Stainless Steel

Wire Arc Additive Manufacturing (WAAM) 316L stainless steel unavoidably introduces defects such as porosity, oxide inclusions, and lack of fusion due to the inherent characteristics of the process. These defects can significantly affect the mechanical properties and service reliability of the material. This study focused on evaluating the defects in WAAM 316L stainless steel by nonlinear ultrasonic testing based on Lamb waves. The effects of FCAW (flux cored arc welding) parameters, including shielding gases (98% Ar + 2% O₂ and 100% CO₂) and welding speeds (20, 30, and 40 cm/min), on the columnar grain, porosity, and defect types were systematically analyzed. The formed specimens were then subjected to nonlinear ultrasonic testing, and the results showed that the ultrasonic nonlinear parameters exhibited high sensitivity to changes in porosity. This suggests that nonlinear ultrasonic testing can effectively assess processing defects in WAAM 316L stainless steel. The findings provide valuable insights for optimizing the WAAM process and improving the reliability of additive manufacturing components.