不同切削距离下硬质合金刀具加工GH4169的切削性能研究

为探索不同切削距离下硬质合金刀具加工GH4169时的磨损规律、切削力、表面粗糙度,对GH4169材料进行了切削试验。分析了硬质合金刀具磨损的演变过程及刀具磨损对切削力、表面粗糙度的影响。研究结果表明,随着切削距离的增加,前刀面磨损区域逐渐扩大,前刀面磨损形式依次为涂层脱落、沟槽磨损、粘附磨损,后刀面磨损形式主要为涂层脱落及微崩刃。高温合金材料中较多的硬质颗粒,及其较强的粘性是导致前刀面磨损的主要原因。F_x、F_y、F_z的总体变化趋势为随着切削距离的增加先增大后减小,试件表面粗糙度随切削距离的增加先减小再增大后减小,在切削75m时,表面粗糙度最小。     

金刚石涂敷刀具在切削过程中的温度测量

本文采用新的测量技术可测定切削时金刚石涂敷刀具前倾面的精确温度分布。该技术可望在确定金刚石涂敷表面热负荷以获得最优切削参数和减少其磨损率、提高经济效益方面发挥作用。此外，它还可用于确定不同涂敷刀具对不同工件的切削加工性能。     

车削45%SiCp/Al复合材料刀具寿命及磨损机制研究

为探索金刚石刀具(PCD)和涂层硬质合金刀具加工45%SiCp/Al复合材料时的刀具磨损、切削力、表面粗糙度的变化规律,对45%SiCp/Al复合材料进行了切削试验。分别使用三向测力仪对切削力进行测量,光学显微镜对刀具磨损进行了观察和测量。分析了PCD和涂层硬质合金刀具磨损的演变过程及刀具磨损对切削力、表面粗糙度的影响规律。研究结果表明,对于PCD刀具,前刀面磨损形式依次为晶粒脱落、磨粒磨损、粘结磨损并存在崩刃。后刀面的主要磨损形式为磨粒磨损,并伴有积屑瘤的产生。硬质合金刀具前刀面磨损形式依次为涂层脱落、磨粒磨损,后刀面出现严重磨粒磨损并且出现粘附现象,用PCD刀具切削45%SiCp/Al复合材料,切削力随积屑瘤增长或脱落呈周期性变化。用涂层硬质合金刀具切削时,主切削力是PCD刀具的两倍。对于PCD刀具,表面粗糙度也随积屑瘤呈周期性变化。涂层硬质合金刀具切削45%SiCp/Al复合材料的表面粗糙度大于PCD刀具,并且随切削距离增加急剧增长。     

单晶硅超精密切削的刀具磨损试验研究

针对单晶硅超精密切削过程中金刚石刀具磨损问题,对单晶硅进行超精密车削试验。通过观察金刚石刀具磨损演变过程,分析刀具的磨损过程对表面加工质量的影响,得到刀具磨损机理。结果表明,在超精密切削单晶硅过程中,随着切削距离的增加,刀具磨损面积逐渐增加,加工过程中产生的碳化硅及类似金刚石碳颗粒与刀具后刀面发生划擦造成磨粒磨损;同时,由于交变载荷作用导致的应力疲劳现象,进而伴有解理断裂产生。当切削路程小于4km时,加工表面的粗糙度Ra值在200nm以内,切削路程大于8km时,表面粗糙度Ra值在350nm~400nm之间。     

机械加工刀具的成分设计与切削性能研究

对比分析了陶瓷刀具和聚晶立方氮化硼刀具在不同切削加工参数下的硬态切削表面性能,并分析了刀具表面的磨损形貌特征。结果表明,陶瓷刀具和立方氮化硼刀具的表面粗糙度都随着切削速度和后刀面磨损程度的增加而降低;随着进给量的增加,陶瓷刀具和立方氮化硼刀具的表面粗糙度逐渐上升;切削深度对刀具表面粗糙度的影响不大。CBN刀具的磨损机制主要为磨粒磨损和氧化磨损。     

表面织构对GCr15淬硬轴承钢切削过程影响分析

针对GCr15淬硬轴承钢切削过程中由于切削力大、切削温度高而导致的刀具磨损加剧问题,在工件表面预置织构,通过有限元仿真结合正交试验对切削过程进行模拟,并通过信噪比分析方法进行优化分析,利用极差分析、方差分析确定最优切削参数组合以及切削参数对于切削力以及温度的影响程度。切削仿真结果表明:切削速度120 m/min、进给量0.05 mm/r、切削深度0.1 mm为最优切削参数组合。在最优切削参数条件下,通过对表面织构GCr15轴承钢进行切削仿真模拟,得到切削力以及切削温度的仿真结果。将表面织构和无表面织构的切削仿真模拟结果进行对比,结果表明表面织构切削仿真的切削力及切削温度都得到有效降低,有利于减少刀具磨损,提高刀具寿命。     

高速切削钛合金的涂层硬质合金刀具粘结磨损

针对粘结磨损对涂层硬质合金刀具使用寿命的影响问题,为了优化刀具涂层材料,降低刀具磨损率,基于热力学理论,计算了硬质合金刀具涂层材料的焓值,分析了涂层材料的耐磨性,研究了涂层硬质合金刀具粘结磨损规律。通过涂层硬质合金刀具切削加工钛合金的实验,使用EDS分析仪和白光干涉仪分别对涂层硬质合金刀具切削加工后的元素能谱和表面形貌进行了分析。结果表明:采用热力学理论分析方法可以获得较好的粘结磨损预测精度,高速切削时刀具磨损区域发生了粘结磨损,磨损原因与元素扩散密切相关;粘结磨损主要发生在中速切削时;随着切削速度的提升,粘结磨损率先增加后降低。所得结论将为优化切削参数、提高刀具寿命提供有益的参考。     

基于切削技术的金刚石刀具磨损特征分析

金刚石刀具的磨损情况决定其使用寿命。用金刚石PCD刀具切削6061-T6镁铝合金工件,通过不同切削速度、切削深度、振动频率、刀具后角时的切削力及切削温度变化,研究不同刀具前后角、进给量、切削转速时的工件表面粗糙度及刀具磨损面积。结果表明:金刚石刀具的切削力和切削温度随切削速度、切削深度的增加而增大,随振动频率的增加而减小;刀具后角增大,金刚石刀具的切削力呈先下降而后缓缓上升趋势,但对切削温度的影响很小。当刀具前角为10°,刀具后角为8°,切削速度为0.46?m/s,切削深度为28?μm,进给量为0.10?mm/r,切削转速为4100?r/min,振动频率为22?kHz,切削振幅为9?μm时,金刚石刀具的磨损面积最小,磨损程度最低,使用寿命最长,但工件的表面粗糙度稍高。      

高温下TiN涂层的摩擦与磨损行为

采用阴极离子镀方法在YT14硬质合金刀具表面制备了Ti N涂层,用高温摩擦磨损试验机考察Ti N涂层在500℃高温下摩擦-磨损行为。通过扫描电镜观察涂层表面-界面形貌和高温磨损后表面形貌,用XRD分析了Ti N涂层物相变化,并用EDS能谱仪对结合界面进行线扫描分析和磨痕进行面扫描分析,同时用工具显微镜观察了表面犁沟形貌,对Ti N涂层500℃下磨损机理进行探讨。结果表明,Ti N涂层在500℃磨损后发生高温氧化,Ti N涂层表面磨痕处主要以Ti O2为主,这些氧化层起到了润滑减摩的作用,适合于高速切削与干式切削;在5 N载荷作用下,Ti N涂层的摩擦系数平均值为0.7116;在高温下Ti N涂层表现为氧化磨损,同时伴随着一定的磨粒磨损和黏着磨损。     

基于热力学的聚晶立方氮化硼刀具切削镍基合金的磨损机理

文章通过切削实验研究了聚晶立方氮化硼刀具切削镍基合金的磨损机理。运用热力学基本理论推导了物质吉布斯自由能函数法,并应用到刀具前刀面氧化磨损的分析中。计算了刀具表面极易发生的化学反应的吉布斯自由能,并分析得出了发生氧化磨损的主要氧化反应方程式。运用扩散第一定律分析了刀具发生扩散磨损的机理,得出了刀具前、后刀面扩散磨损过程发生机理的差异性。运用SEM扫描电镜对刀具表面进行了化学磨损分析。结果表明,刀具前、后刀面都发生了严重的氧化、扩散以及化学磨损,刀具表面发生了严重的放氮反应。研究内容可为加工镍基合金提高刀具寿命提供参考。     

微织构车刀制备与SUS304钢高速微车削试验

针对高速微切削过程中微型车刀表面摩擦磨损严重的问题,利用表面非光滑微织构减摩减阻原理,在高速微切削用车刀表面利用激光加工技术制备了微槽、微坑织构,研究了激光加工参数与微织构形貌之间的关系;分析了微织构的摩擦学特性;利用自行研制的高速微车削单元进行微织构刀具及无织构刀具的高速微切削SUS304不锈钢的对比试验,从切削力、切削温度、刀屑接触状态、切屑形态以及已加工表面粗糙度对微织构车刀性能进行评价。结果表明:微槽、微坑织构均可以有效降低刀具表面摩擦因数;在高速微切削过程中可以减小切削力、切削温度,降低刀屑接触长度,改善切屑形态,尤其是微坑织构可明显改善表面质量,可以应用到SUS304不锈钢的高速微加工。     

Effect of femtosecond laser pretreatment on wear resistance of Al2O3/TiC ceramic tools in dry cutting

A femtosecond pulsed laser (pulse width: 120 fs, wavelength: 800 nm and repetition rate: 500 Hz) was used for the pretreatment on the rake face of Al₂O₃/TiC ceramic cutting tools. The evolution of surface morphology of pretreated cutting tools irradiated with different pulse energies was measured by scanning electron microscope (SEM) and atomic force microscope (AFM). Dry cutting tests were carried out with these pretreated tools and conventional tools on hardened steel. The effect of pulse energy on the wear resistance of these pretreated tools was investigated. Results show that the cutting forces have no significant difference between laser pretreated tools and the conventional tool; the cutting temperatures of laser pretreated tools were slightly reduced compared with the conventional tool. Meanwhile, we found that the laser pretreated tools increased the adhesions of chips on the rake face, but they can significantly improve the wear resistance of the rake face; and laser pulse energy was found to have a profound effect on the wear resistance of the laser pretreated tools.     

Direct laser assisted machining with a sapphire tool for bulk metallic glass

Bulk metallic glasses (BMGs) are amorphous metallic alloys with high strength and hardness. This paper discusses the machining process of Zr-BMG using a transparent sapphire tool with direct laser assistance. The laser beam passes through the tool and directly heats the workpiece material to improve its machinability. Micro textures were generated on the tool rake face to facilitate chip formation. Reduced cutting forces and improved surface finish were observed with direct laser assistance. The effects of machining speed and laser power on the material deformation mechanism were investigated. A finite element model was developed to investigate the cutting forces.     

具有沟槽微织构的超硬材料刀具切削仿真与实验研究

目的 探究微织构置入切削刀具表面对切削性能产生的影响.方法 在具有沟槽微织构的超硬材料刀具上,设计了切削仿真与实验.基于流体动压射流和流体二次润滑,以J-C准则作为车削的本构关系,采用ABAQUS进行仿真.在相同条件下,对有无沟槽微织构的超硬材料刀具进行了三维切削Al6061模拟,并结合刀具应力和前刀面切削温度,对切削性能进行了分析.采用飞秒激光工艺制备了新型沟槽微织构超硬材料车刀,并在CA6136车床上进行单因素切削实验.结果 刀具在置入沟槽微织构后,不仅降低了摩擦副间的接触面积,而且在切削液的双重作用下,瞬时高温现象也得到了缓解.在干切削条件下,沟槽微织构刀具的前刀面不具有较好的减磨抗粘能力,刀具磨损较快.在切削液润滑、流体动压射流现象和沟槽微织构共同作用下,刀具的摩擦磨损状况得到很大改善,使用寿命得到延长.结论 综合切削仿真与实验结果可知,微织构置入切削刀具表面能够提升刀具切削性能并缓解刀具磨损情况.     

喷焊镍基材料切削加工过程的研究

通过选用一批有代表性的典型刀具对喷焊镍基高温合金材料进行刀 具耐用度切削对比试验,找出了各自的耐用度公式,并且还借助于扫描电镜和电子探针观察刀具磨损区,切屑底面和工件已加工表面,由微区形貌和微区成份分析得出其刀具主要为磨粒磨损的结论,这与通常高温镍基合金材料切削时的刀具磨损规律不同。     

Measurement of milling tool vibrations during cutting using laser vibrometry

Spindle and tool vibration measurements are of great importance in both the development and monitoring of high-speed milling. Measurements of cutting forces and vibrations on the stationary spindle head is the most used technique today. But since the milling results depend on the relative movement between the workpiece and the tool, it is desirable to measure on the rotating tool as close to the cutters as possible. In this paper the use of laser vibrometry (LDV) for milling tool vibration measurements during cutting is demonstrated. However, laser vibrometry measurements on rotating surfaces are not in general straight forward. Crosstalk between vibration velocity components and harmonic speckle noise generated from the repeating revolution of the surface topography are problems that must be considered. In order to overcome the mentioned issues, a cylindrical casing with a highly optically smooth surface was manufactured and mounted on the tool to be measured. The spindle vibrations, radial tool misalignment, and out-of-roundness of the measured surface were filtered out from the signal; hence, the vibrations of the cutting tool were resolved. Simultaneous measurements of cutting forces and spindle head vibrations were performed and comparisons between the signals were conducted. The results showed that vibration velocities or displacements of the tool can be obtained with high temporal resolution during cutting load and therefore the approach is proven to be feasible for analysing high-frequency milling tool vibrations.     

Characterization of a hybrid laser-assisted mechanical micromachining (LAMM) process for a difficult-to-machine material

Mechanical micro-cutting is emerging as a viable alternative to lithography based micromachining techniques for applications in optics, semiconductors and micro-mold/dies. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials such as mold and die steels or ceramics, limited cutting tool/machine stiffness and strength are major impediments to the efficient use of mechanical micromachining methods. In addition, at micron length scales of cutting, the effect of tool/machine deflection on the dimensional accuracy of the machined feature can be significant. This paper presents experimental characterization of a novel hybrid laser assisted mechanical micromachining (LAMM) process designed for 3D micro-grooving that involves highly localized thermal softening of the hard material by focusing a solid-state continuous wave laser beam in front of a miniature cutting tool. Micro-scale grooving experiments are conducted on H-13 mold steel (42 HRc) in order to understand the influence of laser variables and cutting parameters on the cutting forces, groove depth and surface finish. The results show that the laser variables significantly influence the process response. Specifically, the mean thrust force is found to decrease by 17% and the 3D average surface roughness increases by 36% when the laser power is increased from 0 to 10 W. The groove depths are found to be influenced by the machine (stage) deflection and tool thermal expansion, which affect the actual depth of cut, in the presence of laser heating. In particular, it is found that the accuracy of groove depth improves with laser heating. Explanations for the observed trends are given.     

The preparation of cutting edges using a marking laser

During the machining process, high mechanical and thermal loads occur at the cutting edge. Such loads can cause tool failure. Specifically non-uniform and sharp cutting edges that have a low cutting edge stability lead to such failures. In order to enhance the tool performance, the cutting edges are prepared by manufacturing both a pre-defined cutting edge geometry, and an appropriate cutting edge roughness. This paper describes the use of a low-cost marking laser for the preparation of cutting edges as an alternative to conventional preparation techniques, such as brushing or blasting. Cutting edge radii of 9?C47 ??m can be prepared with a machining accuracy of 1.5 ??m. The maximum preparation time for an individual cutting edge is approximately 10 s. Uncoated indexable inserts manufactured in this way were tested in a face milling operation. The results of these investigations (using prepared cutting edges) show both an increase in tool life and an improved surface roughness of the machined workpieces compared to those using non-prepared cutting edges.     

基于倍福系统伺服优化的研究

激光切割机是高速、高精度的数控机床,对机床的动态特性及跟随误差要求很高.本文对配置倍福系统的激光切割机进行伺服优化分析,并通过海德汉二维光栅进行圆度测试.测试结果表明影响机床精度的主要因素有伺服参数、减速机反向间隙、机床自身的震动等.     

复合织构刀具切削铝合金的性能∗

基于铝合金材料切削的现状和需求,针对单一织构刀具存在的抗黏减摩性能不足的问题,将不同织构应用于刀-屑接触区域,提出刀具前刀面分区异构的思想。利用皮秒激光在刀具黏结区与滑移区分别加工凹坑和沟槽,并调整沟槽的取向(平行 / 垂直于主切削刃),得到上下型(SXDV 和 SXDP)和左右型(ZYDV 和 ZYDP)四种复合织构刀具。对 6061 铝合金进行湿切削试验,研究不同区域内添加不同织构对刀-屑接触表面摩擦状态的影响。研究结果表明,对比无织构和单一织构刀具, ZYDP 复合织构刀具展现了更好的切削性能。具体表现如下：与无织构刀具相比,ZYDP 刀具的主切削力降低 30.7%,刀面黏结面积减少 63.9%,切屑卷曲半径减少 27.4%。合理的复合织构方案可以明显改善刀具切削过程中的黏结磨损问题,延长了刀具寿命。复合织构方案的提出以及相应的激光加工过程可为织构刀具的设计及实际应用提供新思路。