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Ultrashort pulse laser polishing by continuous surface melting
Journal of Materials Processing Technology ( IF 6.7 ) Pub Date : 2021-01-23 , DOI: 10.1016/j.jmatprotec.2021.117058
Astrid Sassmannshausen , Andreas Brenner , Johannes Finger

Enabling high precision material processing, ultrashort pulse (USP) laser beam sources are increasingly applied in the field of surface structuring. In the mold and die production, three dimensional structures with a vertical depth of a few (10–500) micrometers are created by laser ablation, resulting in a surface roughness Sa = 0.4–2 μm on the 3D structures. Because many applications require a lower surface roughness, a polishing process has to be conducted following the laser ablation.

In terms of a digital photonic process chain including the workpiece’s processing in the same setting for both laser structuring and laser polishing a novel polishing process using USP laser radiation is investigated. In contrast to the customary claim of USP laser processing the aim of USP polishing is to induce a thin molten surface layer. Thus, smoothing is achieved by reallocating material from the peaks to the valleys.

Unlike laser polishing with longer pulse durations melt formation is not determined by the single pulse duration but rather by the temporal and spatial energy distribution. Heat accumulation is achieved by applying a high pulse repetition rate fseed=48.92 MHz at a pulse duration of τ = 800 fs. The purpose of this work is to investigate the influence of USP polishing on surface properties of 1.2738 tool steel including surface roughness, surface topography and microstructure of the remelted surface layer. Originating form an initially ground surface with Sa = 0.6 μm a reduction to Sa = 0.3 μm is achieved revealing a polishing rate of 12.15 cm²/min per pass.



中文翻译:

通过连续表面熔化进行超短脉冲激光抛光

为了实现高精度的材料加工,超短脉冲(USP)激光束源越来越多地应用于表面结构化领域。在模具生产中,通过激光烧蚀可创建垂直深度为几(10–500)微米的三维结构,从而在3D结构上产生表面粗糙度S a = 0.4–2μm。由于许多应用要求较低的表面粗糙度,因此必须在激光烧蚀之后进行抛光工艺。

在数字光子处理链中,在相同的环境下对工件进行激光加工和激光抛光都进行了研究,研究了一种使用USP激光辐射的新型抛光工艺。与USP激光加工的常规要求相反,USP抛光的目的是产生薄的熔融表面层。因此,通过将材料从峰重新分配到谷来实现平滑。

与具有较长脉冲持续时间的激光抛光不同,熔体形成不是由单个脉冲持续时间决定,而是由时间和空间能量分布决定。通过以高脉冲重复频率f seed = 48.92 MHz在脉冲持续时间为τ= 800 fs。这项工作的目的是研究USP抛光对1.2738工具钢表面性能的影响,包括表面粗糙度,表面形貌和重熔表面层的微观结构。从最初的研磨表面开始,S a = 0.6μm,减小到S a = 0.3μm,表明每遍抛光速率为12.15cm²/ min。

更新日期:2021-02-08
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