Automated line-focused laser ablation for mapping of inclusions in stainless steel

An automated line imaging arrangement for two-dimensional (2D) and three-dimensional (3D) generation of chemical maps of inclusions in stainless steel by laser-induced plasma spectrometry (LIPS) is presented. The plasma was generated in air at atmospheric pressure by focusing a flat-top Nd:YAG laser beam operating at 532 nm to a microline on the sample surface. The emitted light from the microline plasma was projected through an imaging spectrograph onto a charge-coupled device (CCD) detector to generate a spatially and spectrally resolved data set. Compositional distribution maps of inclusion constituents (Mn, Mg, Ca, Al, and Ti) in stainless steel of different grades have been generated. Comparative studies with the point-to-point LIPS mapping method have been performed, resulting in a 51-fold reduction in the number of pulses and analysis time when the microline imaging approach is employed. The results illustrate the capability of microline imaging LIPS for fast-automated acquisition of tomographic maps with spatial resolution of 50 microm between adjacent craters and 4.8 microm along the microline.