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.

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Cladding is an alloy layer that is superior in abrasion resistance by spraying, overlay welding, laser cladding or the like on its surface in case of abrasion due to repeated abrasion, impact, corrosion. Laser cladding is a process in which a clad material and a part of a substrate are melted with a high power laser beam to form a coating layer completely metallurgically bonded to the substrate. In this study, laser cladding was performed using Co-based LC-190 alloy powder for hard facing of ship exhaust valve. One-pass cladding was performed by varying the preheating temperature, laser output and beam feed rate of the base material using a diode laser with a maximum output power of 8.0 kW. The shape, dilution rate, Characteristics were observed. As a result, defects could be suppressed by applying preheating, and as the heat input increased, the width of the clad layer increased and the height decreased. In addition, the average hardness value was gradually decreased as a result of hardness measurement, and it was found that dilution was increased by EDS component analysis.