雷达功率组件的金刚石微通道热沉激光加工工艺

为研究雷达功率组件金刚石微通道热沉的加工难题,开展了飞秒激光加工多晶金刚石微流道的工艺研究,仿真模拟了飞秒激光作用于金刚石表面的温度场分布,以及诱导去除过程,理论与实验研究了金刚石的烧蚀阈值,系统研究了激光能量、扫描速度、扫描次数、焦点位置等参量及其优化工艺参数对金刚石微槽尺寸的影响规律。结果表明:当飞秒激光功率大于0.3 W时,激光作用于金刚石的最高温度超过材料去除的气化温度,温度最高位置处于光斑中心,功率不会改变温度场的分布情形;飞秒激光加工金刚石的烧蚀阈值为1.80 J/cm2,金刚石微槽深度与激光功率、扫描次数正相关,与扫描速度负相关,与正负离焦量基本成对称分布关系,而金刚石微槽表面宽度则变化不明显;在激光功率为5 W,扫描速度为100 mm/s,扫描次数为30,离焦量为-0.5 mm的优化参数下,加工出的金刚石微槽结构形状规则,截面侧壁锥度控制在3°以内,表面无残渣、裂纹、崩边等缺陷,且内部也无裂纹等缺陷,加工一致性较高,实现了微通道的 “冷”加工,可满足雷达功率组件金刚石热沉对微通道的高质量加工要求。     

聚晶金刚石的Nd:YAG激光切割与电火花线切割损伤分析

采用近红外Nd:YAG激光切割方法与电火花线切割方法进行了聚晶金刚石(polycrystalline diamond compacts,PDC)切割加工实验,并分别利用细砂纸打磨、金刚石微粉抛光以及王水腐蚀等表面处理方法对试件进行了表面处理,通过扫描电镜显微观察与拉曼光谱分析等方法对试件进行了显微观察与分析。经分析发现:尽管近红外Nd:YAG激光切割速度较快,然而因脉宽较大导致热损伤大,加工表面存在明显的残留层,而且金刚石与硬质合金层界面存在明显的裂纹;电火花线切割表面质量好于激光切割加工,但金刚石界面处存在材料过量去除现象,而且切割速度比近红外激光切割加工小得多。为获得较好的PDC切割质量与切割效率,需采用脉宽更短的Nd:YAG激光或紫外激光。     

飞秒激光烧蚀纳米孪晶金刚石的研究

纳米孪晶金刚石(nt D)材料不仅具有远高于单晶金刚石的硬度,还拥有各向同性、无解理、韧性及高温稳定性好等优越性能,是硬脆材料进行超精密切削时的理想刀具的材料,但是超高的硬度和高温稳定性等特征限制了该材料的广泛应用。为了解决nt D材料的高效率成形和加工问题,通过理论分析和实验研究了飞秒激光加工中nt D材料的去除过程、微槽加工轮廓预测、加工工艺等内容。建立等效脉冲数模型,用于理论计算不同工艺参数对应的阈值能流密度和实际能流密度。最后通过nt D刀具的轮廓加工验证了飞秒激光技术在nt D材料高效率成形加工中的有效性及文中工艺参数研究的合理性。     

CVD金刚石厚膜的制备及厚膜刀具制造技术

分析了沉积参数对合成金刚石厚膜质量的影响,提出了采用燃焰法沉积高质量金刚石厚膜的合理参数,介绍了金刚石厚膜的激光切割、焊接及刃磨加工特性。     

金刚石工具头超声波复合加工的实验研究

研究了金刚石工具头超声波复合加工方法的可行性及加工参数与材料去除率的关系。在研究超声加工，超声复合加工和金刚石工具的基础上，借助SEM分析其典型塑性材料和脆性材料的加工形貌，初步讨论了该方法去除材料的机理。     

CVD金刚石微铣刀的复合加工工艺研究

CVD金刚石具有高的硬度和耐磨性,是制备微铣刀的理想材料。传统的磨削加工制备CVD金刚石微铣刀存在加工效率低的问题。本文提出了一种以激光诱导金刚石石墨化与精密磨削相结合的复合加工工艺来制备CVD金刚石微铣刀的新方法。研究了激光参数对金刚石相变深度和分界线轮廓最大高度的影响,进一步分析了分界线轮廓最大高度对切削刃质量的影响。结果表明,随着单脉冲能量的增加,金刚石相变深度和分界线轮廓最大高度都增大;随着扫描速度的增加,二者都减小,并且减小分界线轮廓最大高度能够提高磨削后切削刃的质量。为了提高制备效率,提出了一种由粗加工和精加工结合的解决方案。通过使用优化后的加工参数,制备出切削刃钝圆半径2.3μm,刀尖圆弧半径3μm的CVD金刚石微铣刀。     

激光强化大直径金刚石圆锯片

应用激光加工技术对金刚石锯片基体进行强化处理,提高了锯片表面硬度和疲劳强度。同时探讨了激光工艺参数对强化效果的影响。     

超硬磨料砂轮的激光修锐技术研究

激光修整超硬磨料砂轮的原理,利用Ｎｄ：ＹＡＧ固体脉冲激光器进行激光修锐青铜结合剂和树脂结合剂硬磨料砂轮的试验,用扫描电镜观察了激光修锐前后砂轮表面的微观表貌,对激光作用下砂轮表面不同结合剂材料的去除机理进行了分析,通过磨削陶瓷试验,研究激光修锐的金刚石砂轮的磨削性能,并与普通砂轮磨削肖修锐的金刚石砂轮进行对比。结果表明,采用试验所确定的激光参数可选择性地去除砂轮表面的结合剂材料,而不损伤超硬磨粒,     

KDP晶体光学零件超精密加工技术研究的新进展

KDP晶体作为优质的非线性光学材料 ,被广泛的应用于激光非线性光学领域。由于大型KDP晶体具有一系列不利于光学加工的特点 ,因此被公认为是最难加工的光学零件。本文概述了KDP晶体超精密磨削和磁流变抛光的加工方法 ,阐述了KDP晶体光学零件单点金刚石加工技术的研究现状 ,并详细地分析了单点金刚石切削加工时机床精度、加工工艺参数、装夹变形、晶格方向变化、金刚石刀具几何参数、冷却液等对加工表面质量 (平面度、表面粗糙度、小尺度波纹等 )的影响     

CVD金刚石涂层工具的水膜辅助脉冲激光加工技术研究

为了揭示水膜层在CVD金刚石涂层磨削工具脉冲激光加工过程中的重铸层抑制作用,基于皮秒脉冲激光加工实验,研究水膜辅助对激光加工重铸层的影响。并在此基础上,采用激光烧蚀实验与理论建模相结合的方法,研究水膜辅助激光功率和扫描速度等加工参数对烧蚀沟槽几何尺寸和形貌特征的影响规律,并验证激光加工理论模型的准确性。结果表明,材料表面形成的水膜层能有效抑制脉冲激光加工重铸层的形成,加工后的材料表面与内部均未发现重铸物质。水膜辅助激光加工实验结果与单纯激光加工理论计算模型吻合度较高,说明水膜层能够有效消除由重铸层引起的激光烧蚀阻碍作用,从而提高激光加工效率。因此,水膜辅助脉冲激光加工技术为新型CVD金刚石涂层磨削工具提供了精密高效的加工方法。     

The mechanism and application of bronze-bond diamond grinding wheel pulsed laser dressing based on phase explosion

This paper presents a theoretical analysis of the surface bond removal mechanism for bronze-bond diamond grinding wheels using a pulsed laser. For the first time, the existence of a phase explosion phenomenon during the process of grinding wheel laser dressing is proposed, and the negative effects of a phase explosion on laser dressing are analyzed. Additionally, a theoretical study on phase explosion is conducted. The mechanism of bronze-bond diamond grinding wheel laser dressing is improved, and theoretical guidance for bronze-bond diamond grinding wheel laser dressing is provided. In the experiment, the processing parameters of the laser during phase explosion are studied, and a grinding test under the corresponding conditions is conducted. A high-speed camera is used to observe phase explosion in the laser dressing process. An ultra-depth 3-D microscope system is used to observe the topography of the bronze-bond diamond grinding wheel after dressing and grinding as well as the bronze wheel surface quality. It is concluded that to avoid phase explosion from occurring in the laser dressing of the bronze-bond grinding wheel, chip space around the bond must exist for the abrasive particle protrusions. The processing parameters of laser dressing under certain condition are optimized, and the desired dressing effect is achieved.     

脉冲激光逐层钎焊金刚石-镍铬合金工艺研究

基于脉冲激光加工时的低能量输入和较小的热影响优势,将其应用到金刚石磨粒的钎焊过程中,以实现多层金刚石磨粒的逐层钎焊成形。通过单道及单层脉冲激光钎焊试验,研究了工艺参数对钎焊成形及对金刚石损伤的影响规律,并优选出较好的工艺参数进行了多层钎焊试验。研究结果表明：在脉冲激光钎焊成形过程中,工艺参数的变化主要通过改变峰值功率密度和线能量密度来影响钎焊成形和金刚石损伤形态。输入的能量密度不足时,钎焊道及钎焊层易出现熔融球、金刚石聚集、熔合不充分、不连续及不平整等现象;输入的能量密度过大时,易出现金刚石损伤、粉末材料及金刚石流失逃逸等现象。当线能量密度为14～25 J/mm²、峰值功率密度在5×10⁵～1.5×10⁶ W/cm²时,可得到平整性良好和金刚石磨粒形态良好的钎焊形貌,且在此参数范围内优选的参数条件下实现了多层结构的逐层钎焊成形,得到了较好的表面成形形态及较低的金刚石损伤形态。多层钎焊试块弯曲试验结果表明,钎焊层与基体之间具有较好的结合强度,未出现钎焊层剥离现象。     

基于有限元的激光定点钎焊温度场研究

利用ANSYS软件对激光定点钎焊过程温度场进行了有限元模拟,在分析过程中采用三维单元,并考虑了材料热物性的非线性特征,建立了有限元模型,得出了钎焊过程中,不同工艺参数下试样表面的温度场分布图,并进行了温度测量和实际钎焊实验。结果表明:有限元分析温度曲线与实测温度曲线比较吻合,钎焊后金刚石与基体实现高强度连接。     

应用CVD金刚石涂层工具研磨单晶蓝宝石

通过热丝化学气相沉积(HFCVD)法制备了具有球状晶结构、棱锥形晶结构和棱柱形晶结构等3种不同表面特征的化学气相沉积(CVD)金刚石涂层工具,以提高其研磨效率。通过正交实验法研究了金刚石涂层晶粒形态、载荷、工作台转速、研磨时间等4个工艺参数对蓝宝石材料去除率和表面粗糙度的影响。结果表明:金刚石涂层的晶粒形态对材料去除率和表面粗糙度影响较大;球状晶结构金刚石涂层切向力较小,棱柱形晶结构金刚石涂层切向力较大;选择棱柱形晶CVD金刚石涂层工具研磨蓝宝石,在研磨加工参数为载荷0.15 MPa、转速100 r/min、研磨时间3 min时,其材料去除率为0.397μm/min,表面粗糙度为0.354μm。结果表明:提出的CVD金刚石涂层工具可用于进一步加工、研磨蓝宝石切片,去除其表面划痕,从而改善工件表面质量。     

Numerical analysis of Nd:YAG pulsed laser polishing CVD self-standing diamond film

Chemical vapor deposited(CVD) diamond film has broad application foreground in high-tech fields.But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications.Laser polishing is a useful method to smooth self-standing diamond film.At present,attentions have been focused on experimental research on laser polishing,but the revealing of theoretical model and the forecast of polishing process are vacant.The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory.The experimental investigation is also carried out on Nd:YAG pulsed laser smoothing diamond thick film.The simulation results have good accordance with the results of experimental results.The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd:YAG pulsed laser.The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields.The temperature at the peak of diamond film is much higher than that in the valley,which leads to the smoothing of diamond thick film.The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out.The results show that high power density laser makes the diamond surface rapid heating,evaporation and sublimation after its graphitization.It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle,moderate laser pulsed energy,large repetition rate and moderate laser pulse width.The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.     

Characterisation of thermal influences after laser processing polycrystalline diamond composites using long to ultrashort pulse durations

The laser processing of cutting tool edges is growing rapidly due to its flexibility, short cycle times and negligible waste. However, the quality of the tool and its cutting edge can vary greatly with different laser parameters and processing strategies. The generation of a graphitic carbon layer and a heat affected zone (HAZ) could occur during laser processing which is expected to reduce the quality and lifetime of the cutting tool. By using focussed ion beam (FIB) techniques to generate a cross section, the graphitic carbon layer and heat affected zone are characterised quantitatively and qualitatively for laser processes and as a reference, lapping and wire electro-discharge machining processes, used in the generation of polycrystalline diamond composite cutting tool edges. A focus is put on laser based techniques which vary in pulse duration from long microsecond pulses down to ultrashort picosecond pulses. A deep insight into the focussed ion beam techniques used and extensive analysis through Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) into the laser–material interactions are presented.     

Recast layer removal using ultrafast laser in titanium alloy

Recast layer, which has undesirable effects on the fatigue resistance and service life of components and microstructures, has been observed and analyzed from the points of surface morphology and internal microstructure by three test methods including scanning electron microscopy, metallographic corrosion analysis, and transmission electron microscopy in this study. In order to reduce the harms of these unwanted recast layers, taking ultrafast laser as a post-machining method for recast material removal is proposed based on the advantages of ultrafast laser micromachining technology, which include the wide material applicability and absence of the recast layer during processing. The feasibility of this new recast layer removal method was verified by experiments on Ti-6Al-4V. With a series of optimized processing parameters, horizontally bedded scanning processing was adopted ultimately in final recast layer removal experiment because of its higher material removal rate and better machined surface quality compared with vertically shifting scanning processing. Based on the theoretical analysis and experimental results, ultrafast laser could be widely applied in more fields of microstructures finish machining.