In the shipbuilding and marine fields, the pre-treatment of painted surfaces for cleaning creates environmental pollution problems. Laser cleaning is an eco-friendly surface pre-treatment process which selectively removing contaminants on a surface by vaporizing them with a laser beam. In this study, a pulse laser was employed to laser clean shop primer and epoxy painted steel plates. The evaporation characteristics of the two paints and the laser cleaning characteristics were analyzed according to the number of laser scans. It was determined that the removal of epoxy paint, which has a relatively low evaporation point, was higher than that of the shop primer paint. In addition, to remove the coating surface and oxide layer while minimizing damage to the base metal, it is important to select the laser cleaning parameters including the number of laser scans.

Laser cleaning technologies have been attracting attention as a solution to the environmental problems caused by pre-treatment processes, but there are very few studies on the removal of paint using laser cleaning. In this study, laser cleaning was performed on steel painted with shop primer and epoxy paint using a Q-switching fiber laser, and the characteristics of the laser cleaned surfaces was compared in relation to the pulse overlap rate, as a main parameter. Experimental results showed that the number of scans to remove the paint decreased as the pulse overlap rate increased. At pulse overlap rates of 20 % and 50 %, the oxide layer was not removed from the surface. However, when the pulse overlap rate was increased to 70%, the oxide layer was completely removed. In addition, damage of the base material was reduced when the pulse overlap rate was increased, more precise laser cleaning was possible.

The quality of metal components manufactured by laser-based additive manufacturing technologies is governed by the process parameters. Moreover, the process parameters differ depending on the material used. In particular, direct energy deposition (DED) technology is vulnerable to the control of external environmental variables, and there are many process variables, such as powder characteristics and laser parameters, and thus many tests are required to determine the optimal parameters. In this study, an experiment was conducted to derive the conformity criterion of the DED process for metal powder (STS304L). First, the effects of laser energy output, laser header moving speed, powder feed rate, and gas feed rate on the DED process were studied. The experimental results showed that the deposition height decreased as the laser header moved faster and that the dilution ratio and the width of the heat-affected zone depended on the laser power and powder feed rate. Specimens were printed based on the process parameter values determined in the experiment, and tensile tests were conducted to analyze their mechanical performance.