Analysis of Microstructural Changes during Pulsed CO2 Laser Surface Processing of AISI 316L Stainless Steel
In the present contribution, a 1.5kW CO2 laser in pulsed wave mode was used to study the effects of laser processing parameters at specific energy fluence. Cylindrical AISI 316L stainless steel samples rotating perpendicular to the laser irradiation direction were used for these experiments. A surface temperature prediction model was implemented to set the experimental process parameters. Laser processing of AISI 316L steel showed a strong correlation between melt pool depth and the residence time at specific fluence levels. At fixed energy fluence, increase in residence time resulted in growth of the melt pool depth. In the melted region, the microstructure was observed to be of more uniform composition and contain fewer impurities. To improve absorption level, samples were etched and roughened. These samples exhibited lower roughness levels compared to the un-treated samples. For a constant fluence level, samples with improved absorption displayed an increase in depth of melt pool at lower peak powers and higher residence time. As the laser beam interaction time increased, the surface roughness of the steel increased for the various pulse energy levels examined. While the structure of the surface was seen to retain a crystal arrangement, grain orientation changes were observed in the laser processed region.
M.S.J. Hashmi, S. Mridha and S. Naher
E. Chikarakara et al., "Analysis of Microstructural Changes during Pulsed CO2 Laser Surface Processing of AISI 316L Stainless Steel", Advanced Materials Research, Vols. 264-265, pp. 1401-1408, 2011