Carbon analysis of steel using compact spectrometer and passively Q-switched laser for laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) is carried out with compact 1064 nm laser and spectrometer components which are suitable for handheld applications. Bursts of ∼0.6 mJ, 5 ns laser pulses are generated by a passively Q-switched laser with a 1 kHz triggered pump diode. The miniature spectrometer with a set wavelength range of ∼188-251 nm has an instrumental broadening at the carbon analyte line, C I 193.09 nm, of less than 36 pm. Analytical calibration curves of C, as well as Cr, Ni, and Si are taken with certified reference samples of iron and steel in an argon purged setup. The net duration of the laser bursts is ∼0.7-1.4 s for a measurement, depending on the number of repetitions on the sample surface. The limit of detection (LOD) is determined to a mass fraction of 34 µg/g for C. High-alloy steels 1.4306 (0.01% C) and 1.4541 (0.035% C) are separated clearly by the LIBS measurement of carbon.