# On the Detection and Removal of Oxides from Laser-Treated Surfaces
## 4 Conclusions  
The presence/absence or quantity of oxides on laser-textured metallic materials can be beneficial or detrimental, depending on the specific application. From this stems the need for oxide detection and control. In this work, two methods for the analysis of oxygen/oxide content--EDS and XRD--were applied on three classes of industrially relevant materials. While there are other techniques suitable for this purpose (e.g., X-ray photoelectron spectroscopy [18; 25], Raman spectroscopy [20; 25], Auger electron spectroscopy [25], or secondary ion mass spectroscopy [25]), this work focused on two techniques widely available in materials laboratories. Laser-textured surfaces present a non-ideal case for such analysis due to their surface roughness and the inhomogeneous spatial distribution of species in the gauge volume, in addition to the oxides being present in small quantities. Therefore, a fully quantitative evaluation was not attempted. Instead, a simplified practical approach was taken, providing relative, semi-quantitative results. By comparing the results obtained on pristine samples and those oxidized by a known process, a distinct boundary between 'clean' and 'oxidized' surfaces can be established, which is specific for each material. For materials with the same type of morphology and measured in the same setup, a relative comparison of the degree of oxidation among treatments with different parameters may be obtained. This can then be used as feedback for the laser treatment process--for the selection of specific process parameters, process modification, or a decision on whether dedicated post-treatment is necessary. The applicability of this procedure using EDS was successfully demonstrated on stainless steel, W and a W-Cu composite, and a Ti alloy. For XRD, the oxide content in the investigated steel and W-based materials was below the detection limit; useful results were only obtained on the Ti alloy. Thus, for these small oxide contents, XRD turned out to be applicable only on a limited range of materials. Also, the nature of the information provided by these techniques differs. While EDS determines the fraction of oxygen as an element, XRD yields the fraction of the oxide as a phase, with the added benefit of identifying the phase's structure. Three techniques for oxide removal were also investigated--annealing in a reducing atmosphere, acid etching, and 'gentle' laser ablation. On the W-based materials, all three methods were proven to be effective in oxide removal. For gentle laser ablation, the dependence of the results on several process parameters, namely the pulse frequency, traverse velocity, and number of passes, was found. The heat accumulation temperature measurements revealed a threshold value of \(\sim\)370 \({}^{\circ}\)C, below which the oxide content values were scattered and above which the oxide was removed in a stable manner. Besides  
Figure 5: Correlation of oxide content after laser cleaning with heat accumulation temperature during laser cleaning. A value of 370 \({}^{\circ}\)C is indicated by the red line as the temperature at which a transition from partial to full oxide removal occurs. the effect on oxide content, the chosen parameters also affected the micromorphology of the textured surface, which can have an influence on the coating adhesion as well. The other two methods did not affect the micromorphology significantly. The selection of a given method can be governed by its availability, effectiveness in oxide removal, experimental demands, effects on micromorphology, etc., and all these aspects would have to be evaluated for a specific application. Conceptualization, [PERSON] ([PERSON]); methodology, [PERSON] ([PERSON]), D.M. and [PERSON]. ([PERSON]); investigation, [PERSON] ([PERSON]), [PERSON] ([PERSON]), D.M., O.P., S.K., M.H., F.L. and V.B.