Infrared laser ablation and atomic emission spectrometry of stainless steel at high temperatures

Laser-induced breakdown spectrometry has been evaluated at high temperatures for stainless steel samples. A Q-switched Nd:YAG laser operating at 1064 nm was used to create a microplasma on an AISI 304L stainless steel sample placed inside a laboratory oven. The steel sample was 51.5 cm away from the focusing lens. The temperature of the samples ranged from 25 to 1200 degrees C. The plasma light was collected by means of a fiber optic bundle, spectrally resolved and then detected by a CCD camera. The effects of sample temperature in the formation of a laser-induced plasma have been studied in terms of its spectral features as well as the morphology of the ablated craters in air at atmospheric pressure. A noticeable dependence of signal emission intensity on sample temperature has been found. Depth profiling of stainless steel samples for several temperature conditions was performed. Results have revealed changes in the superficial composition at temperatures above 600 degrees C due to the formation of a slag layer of variable thickness, mainly composed of chromium, iron and manganese oxides.