Zhang Yanmei, Yu Gang, Tian Chongxin, Li Zhiyong, Shao Jiayun, Li Shaoxia, He Xiuli
Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China.
Materials (Basel). 2022 Mar 26;15(7):2457. doi: 10.3390/ma15072457.
Polyether-ether-ketone (PEEK), with its superior mechanical, chemical, and thermal properties, as well as high biocompatibility, has been used in aerospace, electronics, and biomedical applications. In this paper, a large number of experiments of single-pulse laser drilling on PEEK were performed to analyze the hole morphology and keyhole evolution, which were characterized by an optical microscope, charge-coupled device (CCD), and high-speed camera. A novel method is proposed to observe and measure the dimension of the processed hole rapidly right after laser drilling for special polymer materials with wear-resistance and non-conductivity. Morphological characteristics of holes are presented to illustrate the effect of pulse width and peak power on hole depth, hole diameter, and aspect-ratio. The obtained maximum drilling depth was 7.06 mm, and the maximum aspect-ratio was 23. In situ observations of the dynamic process of laser drilling, including the keyhole evolution together with ejection and vaporization behavior, were also carried out. The keyhole evolution process can be divided into three stages: rapid increment stage (0−2 ms) at a rate of 2.1 m/s, slow increment stage (2−4 ms) at a rate of 0.3 m/s, and stable stage (>4 ms). Moreover, the variation of dimensionless laser power density with the increase in pulse width was calculated. The calculated maximum drilling depth based on energy balance was compared with the experimental depth. It is proven that the laser−PEEK interaction is mainly influenced by a photothermal effect. Ejection is the dominant material-removal mechanism and contributes to over 60% of the depth increment during the rapid increment stage, while vaporization is dominant and contributes to about 80% of the depth increment during the slow increment stage. The results reveal the material removal mechanism for single-pulse laser drilling on PEEK, which is helpful to understand the dynamic process of keyhole evolution. This not only provides a processing window for future laser drilling of PEEK but also gives a guide for the manufacturing of other polymers.
聚醚醚酮（PEEK）具有优异的机械、化学和热性能以及高生物相容性，已被应用于航空航天、电子和生物医学领域。本文对PEEK进行了大量单脉冲激光钻孔实验，以分析孔的形貌和小孔演化过程，采用光学显微镜、电荷耦合器件（CCD）和高速摄像机对其进行表征。针对具有耐磨性和非导电性的特殊聚合物材料，提出了一种在激光钻孔后快速观察和测量加工孔尺寸的新方法。给出了孔的形貌特征，以说明脉冲宽度和峰值功率对孔深、孔径和纵横比的影响。获得的最大钻孔深度为7.06mm，最大纵横比为23。还对激光钻孔的动态过程进行了原位观察，包括小孔演化以及喷射和汽化行为。小孔演化过程可分为三个阶段：快速增加阶段（0−2ms），速率为2.1m/s；缓慢增加阶段（2−4ms），速率为0.3m/s；稳定阶段（>4ms）。此外，计算了无量纲激光功率密度随脉冲宽度增加的变化。将基于能量平衡计算的最大钻孔深度与实验深度进行了比较。结果表明，激光与PEEK的相互作用主要受光热效应影响。喷射是主要的材料去除机制，在快速增加阶段对深度增加的贡献超过60%，而汽化在缓慢增加阶段占主导地位，对深度增加的贡献约为80%。研究结果揭示了PEEK单脉冲激光钻孔的材料去除机制，有助于理解小孔演化的动态过程。这不仅为未来PEEK激光钻孔提供了加工窗口，也为其他聚合物的制造提供了指导。
