摘要
目的解决增材制造GH4169合金表面球化缺陷难以高效、高精度去除的难题,提升增材制造件表面质量与服役性能。方法采用飞秒激光器在氩气气氛下对带有球化缺陷的增材制造GH4169试样进行表面球化缺陷去除实验;基于正交实验设计,研究激光功率、轨迹重叠率LO、光斑重叠率PO及光斑大小df对去除效率与表面质量的影响规律,并结合多手段表征与有限元仿真分析烧蚀机制。结果当激光功率30 W、LO=50%、PO=80%、离焦量≤90µm时,球化缺陷的去除步长达4.65μm且围球化缺陷凹槽式烧蚀损伤最小;累计20次扫描后球化缺陷高度由153.8μm降至20.5μm,基本完成缺陷去除;烧蚀过程中由于球化结构扰动作用形成围缺陷凹槽,深度约9μm。飞秒激光烧蚀有效清除了表面氧化膜,表面O含量(质量分数)由6.67%降至5.58%,Ni、Ti、Cr含量(质量分数)变化<1%;表面硬度从364HV提升至409HV,增幅达12.3%;表面润湿接触角由96.7°降低至82.5°,润湿性显著改善。理论仿真表明,球化结构衍射导致激光能量在球化缺陷边缘能量集中、电场强度呈波纹放射状分布,从而形成了围缺陷凹槽烧蚀。结论飞秒激光烧蚀可针对增材制造GH4169表面球化缺陷实现高效率、高精度的定点去除,同步改善表面硬度与润湿性,对基体成分影响小,为增材制造在线修复提供了可靠技术路径。
GH4169 nickel-based superalloy is widely used in aerospace and other high-end fields;however,selective-laser-melted(SLM)parts frequently exhibit spheroidization defects that severely degrade surface quality and service performance.Conventional post-treatments such as mechanical machining or electropolishing suffer from low efficiency and limited adaptability.The work aims to propose a femtosecond laser spot ablation method to eradicate these spheroidization defects on SLM-GH4169 surfaces,systematically investigate the influences of laser power,pulse/track overlap ratios and defocus distance on removal efficiency,and employ multi-scale characterizations in combination with numerical simulations to unveil the light-field disturbance mechanisms induced by defect topography.Specimens were fabricated on an RS450D metal 3D printer under as-built conditions,presenting spheroidization defects with an average height of 78.4μm.Ablation was performed with an OR-30-IR femtosecond laser under an argon atmosphere.A orthogonal array was employed to optimize laser power,track overlap(LO),pulse overlap(PO)and defocus distance(z),to balance the removal rate against surface quality.Pre-and post-processing topographies,chemistries,hardness and wettability were systematically characterized by laser-scanning confocal microscopy(LSCM),SEM,EDS,XRD,XPS,Vickers micro-indentation and contact-angle goniometry.Optimal removal was achieved at 30 W,LO=50%,PO=80%and defocus≤90μm,yielding a maximum removal step of 4.65μm with minimal peripheral trenching.After 20 passes,the defect height decreased from 153.8μm to 20.5μm,indicating complete elimination.A circumferential groove of about 9μm deep was formed simultaneously,attributed to diffraction of the incident light by the spheroidal topography.COMSOL transient-thermal analyses revealed localized energy concentration at the defect periphery,with temperatures exceeding 2000 K that drove collateral ablation.FDTD simulations further showed a ripple-like,radial intensity distribution within a 50μm annulus around the defect,creating electromagnetic hot-spots responsible for the observed trench.Compositional analyses indicated that surface oxygen decreased from 6.67wt.%to 5.58wt.%after femtosecond ablation,whereas Ni,Ti and Cr varied by<1wt.%,evidencing minimal alteration of the substrate chemistry.XPS confirmed effective removal of the native Al2O3 scale.Vickers hardness rose from 364HV to 409HV(+12.3%)within the processed zone;concomitant XRD peak shifts of theγphase toward higher 2θsuggested lattice contraction and/or micro-strain.Wettability measurements showed a decrease in water-contact angle from 96.7°to 82.5°,restoring a hydrophilic surface favorable for subsequent machining or coating adhesion.In summary,femtosecond laser ablation enables efficient and high-precision elimination of spheroidization defects on GH4169 surfaces while concurrently enhancing surface hardness and wettability,with negligible modification of the bulk composition.The structural disturbance of the incident optical field by the defect topography is identified as the primary mechanism driving the formation of the peripheral trench.This approach offers a reliable laser-subtractive route for in-situ repair and performance enhancement of additively manufactured components,exhibiting excellent scalability and industrial applicability.In the future,integrating in-line monitoring and closed-loop control is expected to further enhance repair accuracy and efficiency.The technology also holds promise for defect remediation in other additively manufactured materials such as titanium alloys and tool steels.
作者
范丽莎
阚星普
喻登宇
张硕文
吴岭
王廷斌
赵天真
张迪
项一侯
姚建华
FAN Lisha;KAN Xingpu;YU Dengyu;ZHANG Shuowen;WU Ling;WANG Tingbin;ZHAO Tianzhen;ZHANG Di;XIANG Yihou;YAO Jianhua(Institute of Laser Advanced Manufacturing,Zhejiang University of Technology,Hangzhou 310023,China;College of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310023,China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment,Hangzhou 310023,China)
出处
《表面技术》
北大核心
2025年第24期79-89,137,共12页
Surface Technology
基金
国家重点研发计划项目(2023YFB4606000)
浙江省“尖兵”“领雁”研发攻关项目(2023C01051)
浙江省属高校基本科研业务费专项资金(RF-C2022001)。
关键词
GH4169合金
球化缺陷
飞秒激光去除
光场扰动
增材制造
GH4169 alloy
spheroidization defects
femtosecond laser removal
light field disturbance
additive manufacturing
