Characterization of laser surface burns generated with different fiber laser parameters: the role of air and nitrogen environments

Abstract This work will discuss the microstructural and magnetic properties of AMS4330 steel resulting from fiber laser surface processing in air and nitrogen shielding atmospheres. Barkhausen Noise (BN) analysis, SEM-EDS, and 3D optical profilometry were employed to investigate how changes in laser parameters influence surface oxidation, roughness, and magnetic stability. Nitrogen shielding considerably reduced the oxidation, obtaining a minimum surface roughness of 0.714 μm at low laser power and scanning speeds, compared with 0.966 μm under similar conditions in air. In full contrast, the air processing reveals severe oxidation with irregular surface texturing, yielding high values of S a up to about 182.15 μm at high laser power and scanning speed. BN analysis indeed revealed the magnetic stability of nitrogen-treated samples, where the Knee point voltage achieved a maximum of 12.140 V, which was relatively higher compared with air treatment, whose maximum is 9.93 V. Confirming this, SEM-EDS also revealed that nitrogen shielding better maintained the elemental integrity through less oxidation of Fe and Ni elements, with minimum oxygen uptakes during such processing, in contrast with general air processing, wherein elemental depopulation occurs along with oxygen enrichments. These results have pointed out the advantages of nitrogen atmospheres for limiting oxidation, surface roughening, and magnetic improvement. This work thus lays a sound foundation for the optimization of laser processing parameters in the quest for improved performance and durability of AMS4330 steel in critical aerospace applications.