Preliminary study on the laser cleaning of stainless steels after high temperature oxidation

The objective of the present work was to estimate the influence of pulsed laser irradiation on the removal of the oxide layer, which is developed on the surface of stainless steels during their exposure to high temperature oxidation. In general, this layer is a protective one, mainly against corrosion. However, in many manufacturing applications or maintenance work, the removal of the oxides is necessary; for example, the metallic surfaces should be cleaned before welding, otherwise the presence of oxides increases the tendency to brittle behaviour of the joint. In this study, a pulsed Nd:YAG laser (λ=1.064 μm, 10 ns) was used for the surface cleaning of three stainless steels with different chemical compositions and/or surface treatments. The influence of the laser irradiation on the material, as well as on the mechanisms involved, was investigated by in-situ mass measurements and post-situ microscopic observations (Scanning Electron Microscopy/SEM, and Energy Dispersion Spectroscopy/EDS). For energy density applied (1.0–2.0 J cm−2), irrespective of the composition and the thickness of the surface layer, the laser irradiation resulted in the expulsion of the oxide layer, while no material removal of the underlying metal occurred.