为了获得纳秒激光除锈工艺规律并揭示除锈机理, 研究了不同工艺参数下激光除锈后AH32船用钢的表面形貌与粗糙度。采用纳秒脉冲激光器在不同工艺参数下对试样表面锈层进行激光清洗, 使用激光共聚焦显微镜测量清洗表面粗糙度, 基于扫描电镜观察清洗表面微观形貌, 借助能谱分析仪进行清洗表面元素分析。最后, 结合试验结果揭示了AH32船用钢的纳秒激光除锈机制。试验结果表明: 在3 000 mm/s的扫描速度下分别采用30.6 J/cm2和10.2 J/cm2的激光能量密度对AH32船用钢表面锈层进行分步激光清洗, 可以显著改善清洗形貌并降低表面粗糙度。微观形貌分析发现在上述清洗条件下, 基体表面呈现微熔状态, 光斑内部光滑均匀, 边缘分布枝晶状乳突结构。分步激光清洗工艺可以获得较好的清洗效果和较高的清洗效率, 其除锈机制主要包括孔洞爆破机制和烧蚀蒸发机制。

To understand the nanosecond laser derusting process and reveal the derusting mechanism, the surface morphology and roughness of AH32 marine steel after laser derusting under different process parameters was studied. First, a nanosecond-pulse laser was used to clean the rust layer of the sample surface under different process parameters. Then, the surface roughness after cleaning was measured using laser scanning confocal microscopy, the micromorphology was measured by scanning electron microscopy, and an elemental analysis was performed using an energy dispersive spectrometer. Finally, the nanosecond laser derusting mechanism of AH32 marine steel was revealed combined with the experimental results. The experimental results indicated that the cleaned morphology was improved, and that the surface roughness was reduced under stepwise laser cleaning with energy densities of 30.6 and 10.2 J/cm2 at a scanning speed of 3 000 mm/s. Moreover, under the above cleaning conditions, the micromorphology of the matrix exhibited a micromelting state after laser derusting, in which the spot was smooth and uniform and the edge of the spot was distributed with a dendritic mastoid structure. It can be concluded that the use of a stepwise laser cleaning process can yield a better cleaning effect and higher cleaning efficiency. The derusting mechanism mainly includes hole blasting and melting-vaporization.