INDUCED BREAKDOWN SPECTROMETRY; INDUCED PLASMA SPECTROMETRY; JEWELRY INDUSTRY; SPECTROSCOPY; METALS; STEEL

In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd: YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laserfluences between 4.3-17.2 J/cm(2) at 532 nm and 2.9-11.7 J/cm(2) at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.

LIBS stratigraphy; Galvanic coatings; Ablation rate; Plasma shielding; Light-plasma interaction; Depth profiling;INDUCED BREAKDOWN SPECTROMETRY; ION-BEAM ANALYSIS; PULSED-LASER DEPOSITION; REDUCED PRESSURE; JEWELRY INDUSTRY; PURE METALS; ABLATION; SPECTROSCOPY; FILMS; THICKNESS

Laser-induced depth profiling was applied to the investigation of galvanised steel sheets as a typical modern multi-layer coating system for environmental corrosion protection. The samples were ablated stepwise by the use of two different wavelengths of a frequency-converted Nd:YAG-laser, 266nm and 532nm, with a pulse duration of tau = 4ns at fluences ranging from F=50 to 250 J cm(-2). The emission light of the resulting plasma was analysed as a function of both penetration depth and elemental spectrum in terms of linear correlation analysis. Elemental depth profiles were calculated and compared to EDX-cross sections of the cut sample. A proven mathematical algorithm designed for the reconstruction of layer structures from distorted emission traces caused by the Gaussian ablation profile can even resolve thin intermediate layers in terms of depth and thickness. The obtained results were compared to a purely thermally controlled ablation model. Thereby light-plasma coupling is suggested to be a possible cause of deviations in the ablation behaviour of Al. The average ablation rate h as a function of fluence F for Ni ranges from 1 to 3.5 mu m/pulse for lambda = 266nm as well as for lambda =532nm. In contrast, the range of h for Al differs from 2 to 4 mu m/pulse for lambda = 532 nm and 4 to 8 mu m/pulse for lambda = 266 nm in the exact same fluence range on the exact same sample. (C) 2016 Elsevier B.V. All rights reserved.