Barkhausen Noise monitoring of microstructure and surface residual stress in maraging steel manufactured by Powder Bed Fusion and aging

Laser Powder Bed Fusion (LPBF) refers to processes conducted layerwise from material powder, which delivers innovative shapes. Nondestructive inspection can significantly benefit LPBF products, considering the tight application requirements. Magnetic Barkhausen Noise (MBN) is an interesting method due to its potential for nondestructive in situ inspections; however, it is still a concern for additively manufactured parts because of their complex microstructure. This study investigated how the MBN signal is influenced by the maraging steel microstructure and surface residual stress in LPBF parts with two build orientations (XYZ and YZX) before and after aging (480 °C for 3 h). Microstructural characterizations were performed with multiple microscopy techniques. Surface residual stress was assessed with X-ray diffraction, and the MBN was collected along two directions (θ0° and θ90°). Different correlation coefficients between surface residual stress and MBN_energy, varying between 0.53 (θ0°) and 0.98 (θ90°), could be mainly explained by surface stress states and some microstructural differences, like the columnar structures and weak crystallographic texture along build orientation. MBN envelope shapes also allow the comprehension of surface residual stress changes undistinguished with the MBN_energy. These findings clarified some potential uses of the MBN for inspecting Laser Powder Bed Fused materials.