石晓波,苏子龙,解恩涵,冯诗和,龙雨,周柱坤.单/双脉冲飞秒激光冲击强化对表面性能的影响[J].表面技术,2025,54(1):228-241.
SHI Xiaobo,SU Zilong,XIE Enhan,FENG Shihe,LONG Yu,ZHOU Zhukun.Effect of Single/Double Pulse Femtosecond Laser Shock Peening on Surface Properties[J].Surface Technology,2025,54(1):228-241 |
| 单/双脉冲飞秒激光冲击强化对表面性能的影响 |
| Effect of Single/Double Pulse Femtosecond Laser Shock Peening on Surface Properties |
| 投稿时间：2024-02-07 修订日期：2024-04-10 |
| DOI：10.16490/j.cnki.issn.1001-3660.2025.01.021 |
| 中文关键词: 飞秒激光冲击 钛 单/双脉冲 表面质量 表面显微硬度 |
| 英文关键词:femtosecond laser shock Ti single/double pulse surface quality surface microhardness |
| 基金项目:国家级大学生创新创业训练计划(202310593029);广西科技基地与人才专项(AA23073019);国家重点研发项目(2021YFE0203500);中央引导地方科技发展资金项目(GKZY21195029) |
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| Author | Institution |
| SHI Xiaobo | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
| SU Zilong | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
| XIE Enhan | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
| FENG Shihe | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
| LONG Yu | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
| ZHOU Zhukun | School of Mechanical Engineering, Guangxi University, Nanning 530004, China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China |
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| 中文摘要: |
| 目的 探究单/双脉冲飞秒激光冲击钛金属对其表面质量和表面硬度的影响。方法 利用飞秒激光对钛金属表面直接进行冲击，通过超景深显微镜、扫描电子显微镜(SEM)、SEM能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度计等仪器，表征和分析样品的微观形貌和力学性能。结果 单脉冲主要产生鱼鳞状结构，双脉冲主要产生凹坑状结构，在相同功率下，单脉冲加工后的表面粗糙度低于双脉冲。重复频率和加工次数的增加能提高低脉冲能量下的表面质量。经低功率飞秒激光冲击后，在钛表面观察到激光诱导周期性结构(LIPSS)，经多次加工后出现了颗粒和团簇等氧化结构。在表面粗糙度Ra低于1.6 μm时，采用双脉冲fs-LSP可将钛表面显微硬度的提高幅度达到42%，并且在极高重复频率(5 MHz，8.1 W)下，表面显微硬度的提升幅度约为85%，而单脉冲fs-LSP的最大提升幅度为32%。在相同参数下，双脉冲能植入更高的残余压应力。增加加工次数能进一步细化晶粒，并在热积累受限时提高残余压应力。结论 脉冲能量及其与材料的作用时间是影响表面形貌和硬度变化的主要因素，它受到激光功率、重复频率和加工次数的综合影响。双脉冲可以有效增大飞秒激光对钛金属表面的冲击压力，从而植入更大的残余压应力。fs-LSP表面硬度的提升来源于加工硬化、细晶强化和氧化层硬化的综合作用。 |
| 英文摘要: |
| Constrained by surface quality, the pressure of shock waves induced during direct impact by low-power femtosecond laser is lower and shallower compared to that by traditional nanosecond laser shock peening (ns-LSP) techniques. However, the energy coupling characteristics of double pulse femtosecond laser can be used to significantly enhance the pressure of shock waves induced by low-power femtosecond laser. Titanium metal was chosen as the research subject, and femtosecond laser shock peening (fs-LSP) process was conducted with a 14 μm spacing grid pattern under conditions of unrestricted layers and the absence of absorbing layers. Through comprehensive analysis of experimental results, it was found that compared to single pulse femtosecond laser, double pulse femtosecond laser significantly increased surface hardness while maintaining high surface quality, even reaching the level of improvement achieved by traditional ns-LSP for titanium metal. This demonstrated the superiority of double pulse femtosecond laser in low-power fs-LSP. The experimental setup was used to investigate the effects of single/double pulse fs-LSP processes on the surface morphology, roughness, and microhardness of titanium metal by characterization methods such as depth-of-field microscopy, microhardness testing equipment, scanning electron microscopy (SEM), SEM energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and acoustic emission signal detection under different laser parameters (repetition rate, laser power, and number of processing cycles). Additionally, the trends in full width at half maximum (FWHM) and residual stress distribution after femtosecond laser shock on titanium surfaces were analyzed, along with the intensity of vibration generated during impact. The energy of femtosecond laser and its interaction time with materials were the main factors affecting changes in surface morphology, depending on the combined effects of pulse number, laser power, repetition rate, and number of processing cycles. Within the range of engineering surface roughness standards, the surface of titanium after single pulse femtosecond laser shock peening mainly exhibited a fish scale-like structure, while the surface after double pulse treatment showed a pit-like structure. The surface roughness of samples processed with single pulse was significantly lower than that of samples processed with double pulse, due to the higher temperature and stronger impact generated during double pulse processing. Following low-power fs-LSP, the formation of laser-induced periodic surface structures (LIPSS) occurred, gradually disappearing with increased processing cycles, resulting in particle and cluster oxide structures under single/double pulse conditions, respectively. Surface roughness increased with laser power. Increasing repetition rate and processing cycles improved surface quality after femtosecond laser peening under low pulse energy conditions, compensating for insufficient thermal flux by extending the interaction time with materials, thereby reducing surface roughness and improving surface quality. The enhancement of surface hardness primarily stemmed from the coordinated effects of work hardening, grain refinement, and oxide layer hardening, with double pulse demonstrating significant advantages. Among samples with surface roughness below Ra 1.6 μm, three times of processing under suitable low-power laser parameters resulted in a maximum increase in surface microhardness up to 42% under double pulse femtosecond laser shock peening (fs-LSP), compared to a maximum increase of 32% for single pulse fs-LSP samples. The degree of oxidation increased significantly with the number of processing cycles, with significantly higher oxidation levels observed for double pulse treated samples compared to single pulse treated samples after one and three cycles, while oxidation levels were nearly identical for both single and double pulse treated samples after five cycles. At extremely high repetition rates and medium power (5 MHz, 8.1 W), the increase in surface microhardness reached 85%. As the number of processing cycles increased, FWHM slightly increased under single pulse, while double pulse treated samples showed a more pronounced increase. Residual stress decreased significantly due to thermal relaxation, reaching –25.6 MPa and –22 MPa after five cycles, respectively, from initial values of –67 MPa and –72.4 MPa after three cycles. Under the same pulse energy and repetition rate, the amplitude of impact vibration during single pulse fs-LSP was 7.377×10–4, while that during double pulse fs-LSP coupled the energy of two sub-pulses, enhancing the amplitude of impact vibration to 1.509×10–3. |
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