Combined Nano- and Microsecond Laser Ablation for Elemental Depth Profiling of Metal Targets by Laser-Induced Breakdown Spectroscopy

Combined nano- and microsecond laser pulses are used for ablation and elemental depth profiling of metal targets down to as deep as 2 mm without any sample treatment. Combination of nanosecond and microsecond pulses allows producing few-mm craters together with inducing plasma close to the bottom of a crater. Laser plasma spectra at different crater depths are used to measure the elemental depth profile of the target. Using a wear-resistant coating (nickel alloy reinforced by tungsten carbide particles) as an example, we demonstrate for the first time that individual tungsten particles can be identified at a depth of up to 2 mm in the coating by the intensity of the tungsten line in the laser-induced plasma spectrum and thus the coating quality can be estimated within few seconds without any sample treatment.