Abstract
The obvious advantages of laser paint removal technology make it a viable alternative to traditional paint removal methods. Infrared nanosecond laser was used to remove paint from car body. The microstructure, composition, surface roughness, hardness and ablative products of the samples were analyzed. The effect of the process combination of laser defocus distance and ambient atmosphere (ambient air, compressed air and inert atmosphere) on the substrate damage and the paint removal effectiveness was explored, and the related mechanism was discussed. Defocus not only changed the fluence of laser spot but also increased the spot diameter. The effect of defocused laser paint removal on the paint and substrate was caused by the superposition of these two factors. The results show that the laser with defocus distance of +4 mm effectively removed the paint in inert atmosphere and has the least adverse effect on the substrate. The content of C element and organic components on the substrate surface was the lowest, and its surface roughness and hardness was very close to the uncoated substrate. Focused laser paint removal in ambient air caused the most serious damage to the substrate. Its surface microhardness increased by 11 HV, and the influence depth reached 37 µm. The mechanism of laser paint removal without auxiliary gas is the superposition of laser plasma effect, laser gasification effect and thermal stress effect. In open atmosphere (compressed air and inert atmosphere), the mechanism of laser paint removal is laser gasification effect and thermal stress effect. This research can provide practical references and theoretical basis for the large-scale industrial application of low/non-damage laser paint removal technology.
Highlights
The surface of a vehicle is painted to avoid body corrosion, decorate and distinguish between different uses
The results showed that laser paint removal is mainly affected by laser vaporization effect, thermal stress effect and laser plasma effect, and the thermal stress effect is the largest
The laser vaporization effect and thermal stress effect had little influence, but they all contributed to the violent chemical reaction and physical change
Summary
The surface of a vehicle is painted to avoid body corrosion, decorate and distinguish between different uses. Compared to the above paint removal methods, laser shows obvious advantages [1], making it a viable alternative to traditional paint removal methods: (1) non-contact depaint, so the substrate is not subject to external mechanical force, damage and chemical pollution; (2) high accuracy and selectivity; (3) controllable and easy to achieve automation; (4) the solid waste is much less than the initial amount of paint and is green and environmentally friendly These advantages are important in applications such as high-end vehicles, rail vehicles and military vehicles where substrate integrity is more strictly required, and it is necessary to ensure that the paint is removed accurately and completely, while the adverse effects on the substrate are negligible. It has been successfully applied in military aerospace and nuclear power and other cutting-edge or special fields [4,5]
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