增强相对铝基复合材料超精密加工表面的影响

采用聚晶金刚石（PCD）刀具对SiC增强铝基复合材料进行超精密车削加工试验,基于原子力显微镜（AFM）、扫描电子显微镜（SEM）和Talysurf-6型轮廓仪对加工表面进行检测和分析.结果表明,S iC增强相的切削变形机理对超精密级加工表面的影响重大（粗糙度Ra为0.025μm）.若增强相在解理面直接被切削刀具切断,则SiC增强相附近区域的表面粗糙度值范围为6~10 nm,故产生超精密级加工表面的可能性大;若增强相以拔出或压入的机理进行切削变形,则不易获得超精密级加工表面.较高的切削速度、较小的进给量、较小的刀具钝圆半径和较大的PCD刀具晶粒度都有助于获得超精密级的加工表面,而背吃刀量对其影响很小.SiC增强相的体积分数和类型也是影响超精密级表面质量的重要因素,增强相体积分数越高,表面质量越差,晶须增强铝基复合材料较颗粒增强铝基复合材料可获得更好的表面质量.     

聚晶金刚石研磨工艺研究新突破介绍

聚晶金刚石（PCD）具有接近天然金刚石的硬度、耐磨性以及与硬质合金相当的抗冲击性，是一种被广泛应用于有色金属和非金属材料精密加工的新型刀具材料。为充分发挥PCD刀具的优良性能，提高加工零件的表面质量，刀具前刀面（PCD表面）需加工成镜面。目前，PCD镜面通常采用树脂基金刚石砂轮进行研磨加工，但由于PCD与所用的金刚石磨料硬度、性质相近，因而与传统的研磨加工有着很大的不同，     

超精密飞刀切削加工表面中频微波纹产生机理

超精密飞刀切削是一种重要的超精密加工手段,安装大飞刀盘的超精密铣床能够加工大口径超精密光学元件,加工表面具有很高的面形精度和很低的表面粗糙度值.但是加工表面普遍存在中频微波纹（空间周期从100μm到300μm,幅值低于0.1μm）,极大影响了光学元件的使用.超精密铣床的主轴旋转精度对加工工件影响很大,尤其是主轴轴线偏转会使安装在大飞刀盘外缘处的刀具产生很大位移.为此,建立了适用于空气静压轴承支撑的立式主轴角位移欧拉动力学方程,推导出方程解析解,得出主轴运动规律及其对表面中频微波纹的影响,并设计实验进行验证.最终给出了抑制中频微波纹的工程措施.     

光学微结构的超精密加工技术

微结构光学元件在光电产品及光通讯产品中的应用日益广泛，采用多轴超精密机床加工光学微结构，可达到亚微米级形状精度和纳米级表面光洁度的高精度水平，详细介绍了光学自由曲面及光学微结构的超精密加工技术，并开发了适合超精加工微型槽和微透镜列阵的刀具轨迹自动生成软件。     

圆柱表面微结构阵列超精密车削加工技术

辊子是光学薄膜模压制造的关键零件,其圆柱表面微结构复杂,表面粗糙度要求也极高.超精密车削成形作为微结构的一种高效加工方式,其加工的可达性、伺服刀具动态特性的制约、海量微结构的加工长时一致性等是高质量辊子微结构加工所需解决的关键问题.本文以圆柱球面微结构阵列为例,从其数学描述入手,分析了刀具几何尺寸、伺服系统动态特性与微结构加工可达性之间的制约关系,并在自主研制的超精密车床和快刀伺服系统上进行了两种球面微结构的加工实验,得到了预期的微结构形貌,并对加工实验中发现的切深不一致现象给出了初步的解释.     

ELID精密磨削钢结硬质合金及其AFM表面形貌分析

对钢结硬质合金（GT35）进行在线电解修整（ELID）精密磨削,对钢结硬质合金难磨机理以及ELID磨削钢结硬质合金的磨削机理进行了分析,并通过原子力显微镜（AFM）对镜面钢结硬质合金表面不同区域进行了微观表面形貌的分析,研究结果表明,采用ELID磨削技术实现对钢结构硬质合质合金零件的精密磨削加工,钢结硬质合金磨削表面粗糙度可达nm级,Ra≤20nm。     

微波等离子体刻蚀处理对金刚石薄膜涂层刀具附着力和切削性能的影响

用HFCVD法在硬质合金（YG6）刀具衬底上沉积金刚石薄膜,用氢微波等离子体刻蚀的方法对衬底进行表面预处理,研究了该预处理技术对WC硬质合金衬底表面成分的影响,进一步探讨了所沉积金刚石薄膜的表面形貌和附着力,并通过难加工材料实际切削试验。研究了所制备的金刚石薄膜涂层刀具的切削性能。试验结果表明,Ar-H2微波等离子体刻蚀脱碳处理是提高金刚石薄膜附着力和改善涂层刀具切削性能的有效预处理方法。     

硬质合金刀具钝圆半径的仿真与实验研究

在切削过程中,合理的钝圆半径不仅可以保证加工零件的表面质量,而且也可以大大延长刀具的使用寿命。本文以前角5°、后角10°的刀具车削45#钢为例,针对硬质合金刀具刃口钝圆半径问题进行了研究,基于Abaqus仿真模拟其加工过程,分析了钝圆半径对于切削温度、切削力和工件表面加工质量的影响。同时完成了相应的车削实验,得出了钝圆半径与刀具寿命的关系。采用仿真分析与实验验证相结合的方法确定了硬质合金刀具合理的钝圆半径,对刀具的设计和生产加工具有重要的参考意义。     

基于薄膜热电偶的超精密车削瞬态切削温度的测量

为了实现超精密车削温度的在线测量,本文研究了一种基于薄膜热电偶的测量瞬态切削温度的方法.以切削刀具的刀尖作为镀制薄膜的基底,通过磁控溅射方法制备了Si O2绝缘薄膜和Ni Cr/Ni Si薄膜电极,制成了带有测温传感器并且可以进行超精密车削加工的PCBN刀具.文中对该薄膜热电偶温度传感器进行了标定,得到其塞贝克系数并采用该刀具对PMMA材料进行了超精密车削加工实验,实验结果表明该方法能够有效地测量出加工过程中的瞬态切削温度.     

盾构刀具硬质合金激光表面处理研究现状

盾构刀具由硬质合金刀头与高强度钢基体钎焊连接而成.硬质合金刀头的过早脱落与过快磨损是影响盾构刀具工作寿命的主要原因.激光技术具有节能、快速、绿色、精确自动化的独特优势.应用激光技术对硬质合金进行表面处理,可提高盾构刀具的可靠性.综述了改善硬质合金性能的激光技术,论述了激光处理对盾构刀具性能的改善情况;详细评述了激光织构技术对硬质合金钎焊性能、表面摩擦性能以及涂层结合强度的改善研究;介绍了激光相变硬化技术对硬质合金表面进行处理,提高硬质合金刀具耐磨性的研究进展;最后对盾构刀具硬质合金表面激光处理的发展趋势进行了分析展望.     

Experimental study on the meso-scale milling of tungsten carbide WC-17.5Co with PCD end mills

Tungsten carbide is a material that is very difficult to cut, mainly owing to its extreme wear resistance. Its high value of yield strength, accompanied by extreme brittleness, renders its machinability extremely poor, with most tools failing. Even when cutting with tool materials of the highest quality, its mode of cutting is mainly brittle and marred by material cracking. The ductile mode of cutting is possible only at micro levels of depth of cut and feed rate. This study aims to investigate the possibility of milling the carbide material at a meso-scale using polycrystalline diamond (PCD) end mills. A series of end milling experiments were performed to study the effects of cutting speed, feed per tooth, and axial depth of cut on performance measures such as cutting forces, surface roughness, and tool wear. To characterize the wear of PCD tools, a new approach to measuring the level of damage sustained by the faces of the cutter's teeth is presented. Analyses of the experimental data show that the effects of all the cutting parameters on the three performance measures are significant. The major damage mode of the PCD end mills is found to be the intermittent micro-chipping. The progress of tool damage saw a long, stable, and steady period sandwiched between two short, abrupt, and intermittent periods. Cutting forces and surface roughness are found to rise with increments in the three cutting parameters, although the latter shows signs of reduction during the initial increase in cutting speed only. The results of this study find that an acceptable surface quality (average roughness R_a<0.2 μm) and tool life (cutting length L>600 mm) can be obtained under the conditions of the given cutting parameters. It indicates that milling with PCD tools at a meso-scale is a suitable machining method for tungsten carbides.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00298-y     

Machining performance of low temperature treated P-30 tungsten carbide cutting tool inserts

Machining studies were conducted on C45 workpiece using both untreated and low temperature treated tungsten carbide cutting tool inserts. The machinability of the C45 steel workpiece is evaluated in terms of flank wear of the cutting tool inserts, main cutting force and surface finish of the machined workpieces. The flank wear of low temperature treated carbide tools is lower than that of untreated carbide tools on machining of C45 steel. The cutting forces during machining of C45 steel is lower with the low temperature treated carbide tools when compared with the untreated carbide tools. The surface finish produced on machining the C45 steel workpiece is better with the low temperature treated carbide tools when compared with the untreated carbide tools.     

Mathematical models to predict surface finish in fine turning of steel. Part II

This paper outlines further experimental development of mathematical models for predicting RMS surface finish in fine turning operation using TiC coated and cemented tungsten carbide throwaway cutting tools. The five independent variables included are: cutting speed, feed, depth of cut, time of cut of tool, nose radius. Using these five variables at different levels an experimental approach, predictive models for tungsten carbide and titanium coated tungsten carbide tools were developed. A sixth variable, 'the type of cutting tool,' was used to develop a single model for both the TiC coated and cemented carbide cutting tools. AIS1 4140 steel was used as workpiece specimen in the experimental work. Stepwise regression analysis was used in developing the models.     

Study on the influential process parameters in machining the austempered ductile iron

Since the machinability data on grade 3 austempered ductile iron is scarce, this experimental work mainly focuses on the impact of machining parameters on cutting force and surface roughness while turning the above work material with cubic boron nitride and tungsten carbide inserts. Parameters like depth of cut, cutting speed and feed were considered in this study when analyzing the machinability of austempered ductile iron. Austempered ductile iron was turned with CBN and coated WC inserts. The response surface methodology was utilized to design the experiments and optimize the cutting parameters for the work material by each of the above inserts. The cubic boron nitride insert performs well as compared to the coated tungsten carbide for turning the austempered ductile iron and it has been concluded by taking lower force and higher surface finish in to consideration. The optimum parameters for turning austempered ductile iron with the cubic boron nitride insert is as follows: 174 meter/minute cutting speed, 0.102 millimeter/revolution feed and depth of cut of 0.5 millimeter.     

An application of goal programming technique in metal cutting

This paper outlines the use of the goal programming technique in selecting levels of machining parameters in a fine turning operation on A1S1 4140 steel using cemented tungsten carbide tools. Goals that are proposed to be achieved are: (i) to finish turning the required depth in one pass, mid (ii) to finish turning within a stipulated time. Constraints used are: R.M.S. surface finish values, cutting horse power of the machine, ranges for cutting speed, feed and depth of cut. A predictive equation to predict the R.M.S. Surface roughness values from the machining variables, cutting speed, feed, depth of cut, and time of cut was used. This mathematical model was developed using stepwise regression analysis on the experimental data for 1/64 in. nose radius cemented tungsten carbide cutting tool. Experiment with the machining variables at different levels were performed to obtain the data. A statistically designed experiment called the rotatable design was used for the experimental design     

Development of ANFIS model and machinability study on dry turning of cryo-treated PH stainless steel with various inserts

This present investigation deals about the machinability comparison of cryogenically treated 15-5 PH stainless steel with various cutting tools such as uncoated tungsten carbide, cryogenic-treated tungsten carbide and wiper geometry inserts. Cryo-treated PH stainless steel is considered as the work material in this investigation and experimental trials were performed under dry turning condition. The machinability aspects considered for evaluation are cutting force (F_z), surface roughness (R_a) and tool wear. The outcomes of experimentation reveal that the tungsten carbide inserts which are cryogenically treated provide improved performance in machining while comparing with conventional and wiper geometry inserts at all machining conditions. The measured cutting force and the observed flank wear were less for the cryo-treated inserts. However, wiper tool produces a better surface finish during machining. An artificial intelligence decision-making tool named Adaptive Neuro Fuzzy Inference System has been evolved to determine the relation among the considered input machining variables and output measures, namely cutting force and surface roughness of the machined surface. An analysis has been performed to compare the results obtained from developed models and experimental results.     

Characterization of tool wear when machining alloy 718 with high-pressure cooling using conventional and surface-modified WC–Co tools

Coolant supplied by high pressure into the cutting zone has shown the lower thermal loads on the tool when machining difficult-to-cut materials as the Alloy 718. In this study, we investigate how the combination of high-pressure cooling and tool–surface modifications can lead to further improvements regarding tool life. The general approach is to enhance the coolant–tool interaction by increasing the contact area. Therefore, we machined cooling features into flank and rake faces of commercially available cemented tungsten carbide inserts. In this way, the surface area was increased by ~ 12%. After the cutting tests, the tools were analyzed by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Compared with conventional tools, the tool modifications reduced the flank wear by 45% for the investigated cutting parameters. Furthermore, we were able to significantly increase the cutting speed and feed rate without failure of the tool. The investigated surface modifications have great potential to enhance the productivity of metal cutting processes.     

Cutting Edge Wear of Tungsten Carbide Tool in Continuous and Interrupted Cutting of a Polymer Composite

An experimental study was conducted to evaluate the performance of C6 tungsten carbide, C2 tungsten carbide, and Polycrystalline Diamond (PCD) inserts in cutting Graphite/Epoxy (Gr/Ep) composites. Continuous and interrupted cutting tests under dry conditions were made to cut woven fabric and tape Gr/Ep composites. It was found that continuous cutting mode and high cutting speeds significantly reduce tool life of carbides. Machining of tape Gr/Ep reduces the tool life more than the machining of fabric work pieces. Also, C2 grade carbide inserts had a longer tool life than C6 carbide inserts despite the type of work piece or machining condition used. It was observed that a PCD insert's life was about 100 times of C2 carbide inserts during continuous cutting and at high speeds.     

炭/炭复合材料切削加工试验研究

探讨了Ｃ／Ｃ复合材料结构和机构物理性能的特殊性及机构切削加工的特点。用ＳＥＭ观察了不同切削条件下切屑的断口形貌。用５种不同的刀具材料、刀具角度及几何开头相同的刀具，在一定的切削工艺参数条件下，对该材料进行切削试验，以刀具有前刀面和／或后刀面的磨损率为判据，最佳刀具材料为ＹＧ８，在切削Ｃ／Ｃ复合材料的过程中，轨具的磨损极为严重，刀具磨损的主要机理是粘着磨损和磨粒磨损。     

A study of the tool life of TiC and TiC plus Al2O3 chemical vapour deposited tungsten carbide tools

Tool life characteristics were investigated for tungsten carbide cutting tools coated with TiC and with TiC plus Al₂O₃. A low carbon steel workpiece was turned on a lathe at a feed rate of 0.206 to 0.410 mm rev^–1 and a depth of cut of 0.1 to 0.5 mm for cutting velocities between 100 and 250 m min^–1. Data were analysed using both Taylor's tool life equation and Wu's tool life method. Results were similar for both methods but Wu's method seemed to give more consistent results. Compared to an uncoated tungsten carbide tool, the tool life of both the coated tools were from 5 to 7 times longer and the improvement was greater at higher cutting speeds. The TiC plus Al₂O₃ coated tool was slightly superior to the TiC coated tool. The wear mechanism and a possible explanation of increased tool life for the coated tools are discussed.