Abstract Femtosecond (fs) laser ablation has been studied for the potential of fast, high precision machining of difficult-to-machine materials like binderless tungsten carbide. Obstacles that have limited its efficiency include melting from heat accumulation (HA), particle shielding, and plasma shielding. To address HA without shielding effects, high repetition rate (57.4 MHz), ultra-low fluence fs laser irradiation is performed to study the incubation effect and subsequent HA-ablation threshold of fine-grained tungsten carbides. Exposure times on the order of 100 ms were conducted in air with fluences (1.82 to 9.09 mJ/cm2) two orders of magnitude below the single fs pulse ablation thresholds reported in literature (0.4 J/cm2). Heat accumulation at high repetition rate explains the ultra-low fluence melt threshold behavior resulting in melt crowns around ablated holes and grooves. The results of this study aid in predicting heat buildup in high repetition rate laser irradiation for applications that wish to achieve high ablation rates of difficult-to-machine, ultrahard materials and help enable shaping of binderless tungsten carbide for use in applications too extreme for bindered tungsten carbide.

中文翻译：

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钴结合剂和无结合剂碳化钨中的高重复率飞秒激光热积累和烧蚀阈值

摘要 飞秒 (fs) 激光烧蚀已被研究用于快速、高精度加工难加工材料（如无粘结剂碳化钨）的潜力。限制其效率的障碍包括热积聚 (HA) 熔化、粒子屏蔽和等离子体屏蔽。为了解决没有屏蔽效应的 HA，高重复率 (57.4 MHz)，超低能量 fs 激光照射被用来研究细粒碳化钨的孵化效应和随后的 HA 烧蚀阈值。在空气中进行 100 ms 数量级的曝光时间，通量（1.82 至 9.09 mJ/cm2）比文献中报道的单 fs 脉冲消融阈值（0.4 J/cm2）低两个数量级。高重复率下的热量积累解释了超低通量熔体阈值行为导致烧蚀孔和凹槽周围的熔体冠。这项研究的结果有助于预测高重复率激光照射中的热量积聚，适用于希望实现难以加工的超硬材料的高烧蚀率的应用，并有助于使无粘结剂碳化钨成型，以用于对粘结剂过于极端的应用。碳化钨。