Influence of ns-Laser Cleaning Parameters on the Removal of the Painted Layer and Selected Properties of the Base Metal

Abstract

The removal of the surface paint of Q345 (Gr·B) steel, as well as microstructure and hardness of the cleaned surface were investigated. The laser source used in this study is a nanosecond pulsed Gaussian light source. The surface morphology and microstructure were characterized by a scanning electron microscope and electron back-scattered diffraction. A hardness test was used for capturing variations of the parameter of the cleaned region in comparison to the base metal. The results show that when the X-scanning speed was 1500 mm/s and Y-moving speeds was 7 mm/s during ns-laser cleaning, respectively, the cleaned surface was relatively flat and there was only a few small residual paint. In addition, the contents of Fe and C elements on the cleaned surface reached to 89% and 9%, respectively. Moreover, the roughness was the lowest of 0.5 μm through the observation of the three-dimensional topography. In addition, a fine grain layer appeared on the cleaned surface after laser cleaning at the X-scanning speeds of 500 mm/s and 1000 mm/s. The maximum hardness of the fine grain layer was more than 400 HV, higher than the base metal.

Angular Laser Cleaning of Aluminum Al-4004 with Different Spot Sizes

“…the behaviour of the curves shows that, by increasing the power the hardness value increases, the reason behind such behaviour for aluminum alloy can be explained as follows: first) when laser power density increases, the temperature at the surface metal increases too, due to the absorption of the laser energy, this increase of the temperature allows the structure of the alloy to be harder. Furthermore, second) the rise in the hardness value with the rise of the power might be due to the melting of the alloy's surface layer, causing decreases of silicon particles size below the critical size to fracture, strengthening the Al-Si alloy [23,24].…”

Investigation of paint removal by atmospheric pressure plasma jet

“…In the aviation field, aircraft are inevitably affected by external body collision and airflow scouring during flight, resulting in different forms of damage such as cracking, aging, and peeling of the paint layer [1]. Thus, it is necessary to clean the damaged paint layer to facilitate the detection of possible formed defects like corrosion or cracks on the Al alloy substrate [2] and ensure that the new paint layer has enough adhesion during repainting to prevent cracking from the Al alloy matrix. Generally, civilian aircraft need 2-5 repetitions of overall paint removal and repainting within the service cycle, and military aircraft need paint removal and repainting of the damaged paint after a few hours of flight [3,4].…”

“…The main drawbacks of these technologies are the liquid and gas wastes, which cause environmental pollution, increase cleaning cost and bring about a certain risk of deformation due to the stresses of mechanical cleaning or being corroded by chemical substances. Recently, several improved methods such as ultrasonic cleaning [10], laser cleaning [2] and atmospheric pressure plasma cleaning have been proposed. However, each method also has a particular deficiency.…”

Research Progress and Challenges in Laser-Controlled Cleaning of Aluminum Alloy Surfaces

“…Therefore, the surface of equipment made of aluminum alloy must be repainted often. Before spraying, a paint-stripping procedure must be carried out, and the substrate should not be harmed [ 10 , 11 ]. For instance, an aircraft needs to be overhauled regularly (typically every 5 to 6 years).…”