Eddy current testing of artificial submillimeter internal holes in laser powder bed fusion manufactured alloys

Laser powder bed fusion (LPBF) is one of the important processing methods for additive manufacturing (AM). However, the application of manufactured parts is limited by internal defects, thus hindering the development of the AM industry. Eddy current testing (ECT) technology plays a pivotal role in the detection of AM parts with micro defects due to the advantages of non-destructive and non-contact. In this work, an extremely small differential probe is designed, and the eddy current detection of submillimeter hole defects in three typical alloys (AlSi10Mg, Ti6Al4V and GH4169) is studied numerically and experimentally. A simulation model of ECT is established to investigate the effectiveness of the designed probe in detecting internal holes with diameters of 90, 150, 200 and 250 µm. First, the impact of excitation frequency and coil spacing on defect detection of the designed differential probe is investigated, providing theoretical guidance for differential probe design. The simulation results show that the designed probe can effectively detect defects in internal holes with a diameter of 90 µm, and that the normalised resistance of the three alloys increases with the increase in the hole diameter. Furthermore, internal hole defect samples of three typical alloys and a similar structure probe are fabricated, and the accuracy of simulation results is verified by experiments. Finally, the functional relationship between the size of internal hole defects and the EC response signal of three different alloys is investigated. Laser powder bed fusion is one of the important processing methods for additive manufacturing (AM). However, the application of manufactured parts is limited by internal defects. Eddy current testing (ECT) technology plays a pivotal role in the detection of AM parts with micro defects due to the advantages of non-destructive and non-contact. In this work, an extremely small differential probe is designed, and the eddy current detection of submillimeter hole defects in three typical alloys is studied numerically and experimentally. First, a simulation model of ECT is established to investigate the effectiveness of the designed probe in detecting internal holes with diameters of 90, 150, 200 and 250 µm. The simulation results show that the designed probe can effectively detect defects in internal holes with a diameter of 90 µm, and that the normalized resistance of the three alloys increases with the increase in the hole diameter. Furthermore, internal hole defect samples of three typical alloys and a similar structure probe are fabricated, and the accuracy of simulation results is verified by experiments. Finally, the functional relationship between the size of internal hole defects and the EC response signal of three different alloys is investigated.