PCD刀具连续切削花岗岩的性能研究

用三种不同晶粒尺寸的自制PCD刀具,在三种切削速度下进行了花岗岩的湿式连续切削试验。对刀具前、后刀面的显微形貌特征进行了观测,分析了刀具失效机理,比较了不同晶粒尺寸及不同切削条件下刀具的切削寿命。对刀具后刀面磨损的测量结果表明,在三种切削速度下,粗颗粒PCD刀具显示出更长的刀具寿命;随着切削速度的增加,三种刀具的寿命都有所下降。SEM二次电子图像显示,PCD010和PCD005刀具的磨损机制为硬质点的机械磨损,而晶粒较粗的PCD030刀具的主要磨损机制为机械磨损,同时伴有穿晶磨损。     

Machinability issues in turning of Al-SiC (10p) metal matrix composites

The paper presents the results of an experimental investigation on the machinability of fabricated aluminum metal matrix composite (A356/SiC/10p) during continuous turning of composite rods using medium grade polycrystalline diamond (PCD 1500) inserts. MMC’s are very difficult to machine and PCD tools are considered by far, the best choice for the machining of these materials. Experiments were conducted at LMW-CNC-LAL-2 production lathe using PCD 1500 grade insert at various cutting conditions and parameters such as surface roughness, specific power consumed, and tool wear were measured. Machining was continued till the flank wear land on the tool crossed 0.4 mm. The influences of cutting speed on the insert wear and built-up edges (BUEs) formation were studied. The present results reaffirm the suitability of PCD for machining MMCs. Though BUE formation was observed at low cutting speeds, at high cutting speeds very good surface finish and low specific power consumption could be achieved.     

钛合金切削加工中刀具寿命和刀具磨损的研究

钛合金是典型的难加工材料,提高钛合金的加工效率和刀具寿命是急需解决的问题。本文选用Ti-6Al-4V作为工件材料,选取两种不同的硬质合金和一种聚晶金刚石(PCD)作为刀具材料,对切削加工中刀具寿命和刀具磨损进行了试验研究。研究结果表明:PCD刀具寿命明显高于硬质合金刀具,在高速下优势尤其明显;两种硬质合金刀具低速下主要是粘结磨损,高速下主要是粘结磨损、扩散磨损和氧化磨损;PCD刀具主要是微崩刃和石墨化引起的沟槽磨损。     

The effect of cutting parameters and cutting tools on machining performance of carbon graphite material

Abstract

The present study focuses on the effects of cutting speed, feed rate and cutting tool material on the machining performance of carbon graphite material. Polycrystalline Diamond (PCD) cutting tools are used in machining experiments and its performance is compared with the tungsten carbide (WC) and Cubic Boron Nitride (CBN) tools. Machining performance criteria such as flank and nose wear and resulting surface topography and roughness of machined parts were studied. This study illustrates that feed rate and cutting tool material play a dominant role in the progressive wear of the cutting tool. The highest feed rate and cutting speed profoundly reduce the tool wear progression. The surface roughness and topography of specimens are remarkably influenced from the tool wear. Major differences are found in the wear mechanisms of PCD and WC and CBN cutting tools.     

PCBN刀具高速切削抗氢钢HR-2的性能研究

采用不同CBN含量和晶粒结构的PCBN刀具,在不同切削速度下进行了HR-2抗氢钢的高速精密切削试验。通过对PCBN刀具前、后刀面的显微形貌特征进行观测,分析了刀具的失效磨损机理,研究了不同CBN含量及不同切削速度对刀具使用寿命的影响。对刀具磨损的测量结果表明,PCBN刀具高速切削HR-2时,CBN含量高的刀具显示出更长的使用寿命,且在130-200m/min区间为最佳切削速度区域。SEM和EDS分析结果表明,高速精密切削HR-2的磨损机理为氧化磨损、扩散磨损、粘结磨损,同时存在磨粒磨损以及引起的微崩刃现象。     

聚晶金刚石刀具切削各向同性热解石墨过程中的磨损机理

针对各向同性热解石墨切削过程中刀具磨损过快的问题,采用聚晶金刚石（PCD）刀具进行了切削加工试验。研究了切削过程中PCD刀具的磨损形式、磨损规律以及刀具磨损对表面加工质量的影响。试验结果表明：PCD刀具磨损主要发生在后刀面上,磨损形式为磨粒磨损和氧化磨损。磨损区域可以分为平行沟槽和严重磨损两种形貌。初始磨损阶段,磨损带长度急剧增大,并在切削1200m后进入正常磨损阶段。切削过程中还出现了石墨切屑在磨损区域的黏附堆积和刀具崩刃现象。切削初期,随着切削距离的增大,加工表面粗糙度值急剧增大,切削距离为600m时表面粗糙度达到最大值1.7μm。     

Enhancing Tool Life in High-Speed Machining of Compacted Graphite Iron (CGI) Using Controlled Modulation

The application of controlled, low-frequency modulation superimposed onto the cutting process??modulation-assisted machining (MAM)??is shown to be quite effective in reducing the wear of cubic boron nitride (CBN) tools when machining compacted graphite iron (CGI) at high machining speeds (>500?m/min). The tool life is at least one order of magnitude greater than that in conventional machining. The improvement in wear performance is a consequence of a reduction in the severity of the tool?Cwork contact conditions in MAM: reduction in intimacy of the contact, formation of discrete chips, enhanced fluid action, and lower cutting temperatures. The propensity for thermochemical wear of CBN, the principal wear mode at high speeds in CGI machining, is thus reduced. The MAM configuration employing feed-direction modulation appears feasible for implementation at high speeds and offers a potential solution to this challenging class of industrial machining applications.     

Micro cutting of tungsten carbides with sem direct observation method

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism of tungsten carbides and the behavior of WC particles in the deformation zone in orthogonal micro cutting. Other purposes are to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, machined surface and tool wear rates by the outer turning of this alloy carried out using the PCD cutting tool during these various cutting conditions. A summary of the results are as follows : (1) From the SEM direct observation in cutting the tungsten carbide, WC particles are broken and come into contact with the tool edge directly. This causes tool wear in which portions scrape the tool in a strong manner. (2) There are two chip formation types. One is where the shear angle is comparatively small and the crack of the shear plane becomes wide. The other is a type where the shear angle is above 45 degrees and the crack of the shear plane does not widen. These differences are caused by the stress condition which gives rise to the friction at the shear plane. (3) The thrust cutting forces tend to increase more rapidly than the principal forces, as the depth of cut and the cutting speed are increased preferably in the orthogonal micro cutting. (4) The tool wear on the flank face was larger than that on the rake face in the orthogonal micro cutting. (5) Three components of cutting force in the conventional turning experiments were different in balance from ordinary cutting such as the cutting of steel or cast iron. Those expressed a large value of thrust force, principal force, and feed force. (6) From the viewpoint of high efficient cutting found within this research, a proper cutting speed was 15 m/min and a proper feed rate was 0.1 mm/rev. In this case, it was found that the tool life of a PCD tool was limited to a distance of approximately 230 m. (7) When the depth of cut was 0.1 mm, there was no influence of the feed rate on the feed force. The feed force tended to decrease, as the cutting distance was long, because the tool was worn and the tool edge retreated. (8) The main tool wear of a PCD tool in this research was due to the flank wear within the maximum value of V_max being about 260 μ.     

Cutting forces, chip formation, and tool wear in high-speed face milling of AISI H13 steel with CBN tools

High-speed face milling experiments of AISI H13 steel (46–47 HRC) with cubic boron nitride (CBN) tools were conducted in order to identify the characteristics of cutting forces, chip formation, and tool wear in a wide range of cutting speed (200–1,200 m/min). The velocity effects are focused on in the present study. It was found that, at the cutting speed of 800 m/min, which can be considered as a critical value, relatively low mechanical load, relatively low degree of chip segmentation, and relatively long tool life can be obtained at the same time. Both the cutting forces and the degree of chip segmentation firstly decrease and then increase with the cutting speed, while the tool life exhibits the opposite trend. By means of analyzing the wear mechanisms of tools tested under different cutting speeds, it was found that, as the cutting speed increases, the influences of fracture and chipping resulting from mechanical load on tool wear were reduced, while the influences of adhesion, oxidation, and thermal crack accelerated by high cutting temperature became greater. There exist obvious correlations among cutting forces, chip formation, and tool wear.     

PCD和硬质合金刀具车削钛基复合材料时刀具磨损特征研究

以原位生成晶须和颗粒混合增强钛基复合材料为车削对象,在切削速度为60~120m/min的条件下,对聚晶金刚石（PCD）和硬质合金刀具开展了车削性能试验研究。研究表明,PCD刀具的切削力为硬质合金刀具的77%～88%,其切削温度为硬质合金刀具的65%～82%。无论是高速切削,还是低速切削,PCD刀具都经历初期剧烈磨损而后稳定磨损的过程,而硬质合金刀具仅有急剧磨损的过程。刀具磨损特征方面,PCD刀具主要发生磨粒磨损和黏结磨损,硬质合金刀具主要发生月牙洼磨损、黏结磨损和扩散磨损。     

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al₂O₃ PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.     

The effects of cutting parameters on tool life and wear mechanisms of CBN tool in high-speed face milling of hardened steel

High-speed face milling of AISI H13 hardened steel is conducted in order to investigate the effects of cutting parameters on tool life and wear mechanisms of the cubic boron nitride (CBN) tools. Cutting speeds ranging from 400 to 1,600 m/min are selected. For each cutting speed, the metal removal rate and axial depth of cut are fixed, and different combinations of radial depth of cut and feed per tooth are adopted. The tool life, tool wear progression, and tool wear mechanisms are analyzed for different combinations of cutting parameters. It is found that for most of the selected cutting speeds, the tool life increases with radial depth cut and then decreases. For each cutting speed, the CBN tool life can be enhanced by means of adopting suitable combination of cutting parameters. When the cutting speed increases, the normal wear stage becomes shorter and the tool wear rate grows larger. Because of the variations of cutting force and tool temperature, the tool wear mechanisms change with different combinations of cutting parameters even at the same cutting speed. At relatively low cutting speed, in order to acquire high tool life of the CBN tool, the tool material should possess sufficient capability of resisting adhesion from the workpiece. When relatively high cutting speed is adopted, retention of mechanical properties to high cutting temperature and resistance to mechanical impact are crucial for the enhancement of the CBN tool life.     

Wear of Ceramic Cutting Tools in Ni-Based Superalloy Machining

The machining performance of monolithic and composite silicon nitride and Al₂O₃-based cutting tools in continuous turning of Inconel 718 was examined. The character of tool wear has been found to vary, depending on the feed rate and cutting speeds. At a lower cutting speed, of 120 m/min, tool life is restricted by depth-of-cut notching, while at high cutting speeds (300 m/min), tools fail due to nose wear and fracture. The sensitivity of monolithic Si₃N₄ and Al₂O₃ to depth-of-cut notching was found to he significantly reduced with the addition of SiC whiskers, and to a lesser extent with TiC particulates. The ceramic composites also exhibited resistance to nose and flank wear that was higher than that of the monoliths. The internal stress distribution for the cutting tool has been calculated using the finite element method and is the basis for explaining fracture beneath the rake face. Cutting tool wear results are discussed in terms of chemical and mechanical properties of the ceramic tool material, abrasive wear, thermal shock resistance, and metal cutting conditions.     

Finish Machining of Nickel-Base Inconel 718 Alloy with Coated Carbide Tool under Conventional and High-Pressure Coolant Supplies

Single-point turning of Inconel 718 alloy with commercially available Physical Vapour Deposition (PVD)-coated carbide tools under conventional and high-pressure coolant supplies up to 20.3 MPa was carried out. Tool life, surface roughness (Ra), tool wear, and component forces were recorded and analyzed. The test results show that acceptable surface finish and improved tool life can be achieved when machining Inconel 718 with high coolant pressures. The highest improvement in tool life (349%) was achieved when machining with 11 MPa coolant supply pressure at higher speed conditions of 60 m · min^?1. Machining with coolant pressures in excess of 11 MPa at cutting speeds up to 40 m · min^?1 lowered tool life more than when machining under conventional coolant flow at a feed rate of 0.1 mm · rev^?1. This suggests that there is a critical coolant pressure under which the cutting tools performed better under high-pressure coolant supplies.

Cutting forces increased with increasing cutting speed due probably to reactive forces introduced by the high-pressure coolant jet. Tool wear/wear rate increased gradually with prolonged machining with high coolant pressures due to improved coolant access to the cutting interface, hence lowering cutting temperature. Nose wear was the dominant tool failure mode when machining with coated carbide tools due probably to a reduction in the chip-tool and tool-workpiece contact length/area.     

高速铣削近α钛合金的切削温度研究

切削温度不仅直接影响刀具的磨损和耐用度,而且也影响工件的加工精度和已加工表面质量。由于钛合金导热性差和化学亲和性强等原因,通常在其切削加工时切削温度高、刀具磨损严重,致使切削速度难以进一步提高。本文重点对钛合金高速铣削时的切削温度进行试验研究,阐明夹丝半人工热电偶法测温原理和所测热电势信号的物理意义。试验选用了3种不同类型的硬质合金刀具,系统地研究了切削用量、冷却条件及刀具磨损等因素对近α钛合金高速铣削时切削温度的影响。     

An investigation of heat partition and tool wear in hard turning of H13 tool steel with CBN cutting tools

This paper presents results of an investigation into the tool life and the tool wear behaviour of low content CBN cutting tools used in hard turning of hardened H13 tool steel. The approach followed here required both experimental work and finite element thermal modelling. The experiments involved measuring the cutting forces, cutting temperatures, tool wear, and the contact area. Using the measured cutting forces and the contact area in the orthogonal cutting model, we calculated the heat flux on the tool and applied it in the FE thermal analysis. The temperatures history from the analysis was matched with the experimental data to estimate the fraction of heat entering the tool for both conventional and high speeds. The heat partition into the tool was estimated to be around 21–22% for conventional speeds, whereas for high-speed turning, it was around 14%. The tool wear, however, was found to be dominated by chipping for both cutting speeds and could be reduced considerably by reducing the amount of heat entering the tool.     

EFFECTS OF CUTTING SPEED WHEN TURNING AGE HARDENED INCONEL 718 WITH PCBN TOOLS OF BINDERLESS AND LOW-CBN GRADES

Application of polycrystalline cubic boron nitride (PCBN) tools as an alternative for ceramic and cemented carbide tools in machining superalloys has been frequently identified as a solution for enhancing process efficiency but only a limited number of studies has been done in this area. The current study explores the effect of the cutting speed, which was varied in a wide range (2–14 m/s), on machinability of age hardened Inconel 718 with PCBN tools. Performance of binderless PCBN grade and grade with low-cBN content was evaluated in terms of tool life, tool wear, cutting forces and surface quality. Chip formation and process dynamics were analyzed as well. It was found that low-cBN grade provided 70–90% better surface finish and tool life than the binderless at moderate speeds (5–8 m/s). Performance of both grades at low and high speed ranges was non-satisfactory due to notching and flaking respectively. At low cutting speed adhesive wear plays a major role while as the speed increases a chemical wear becomes dominant.     

Cutting forces and wear in dry machining of Inconel 718 with coated carbide tools

In the machining of heat resistant super alloys used in aeronautical applications and classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by using coated carbide tools at high cutting speeds. To achieve this goal, different coated tools and different cutting conditions were tested in dry conditions. The elementary orthogonal cutting process was chosen, the cutting and feed cutting forces components were measured and the cutting force ratio calculated. This ratio is shown to be as an interesting indicator of tool wear. The tool wear mechanisms tool were analysed by using white light interferometer and scanning electron microscopy coupled to an energy-dispersive X-ray spectroscopy EDS-system. The EDS was very useful to analyse the elements deposited on the cutting tool faces. The ability of the different coatings to increase the carbide tool performance were analysed, the main wear modes were depicted. An optimisation of the cutting conditions was finally proposed and the efficiency of the coatings was shown. The results coming from uncoated tools were compared with those obtained with coated tools under the same conditions of machining. At the end, a choice of coatings is proposed and an extension of this study to an industrial machining operation is presented for future developments.     

超声振动切削SiCp/Al复合材料的刀具磨损试验

分别采用超声切削和普通切削两种方式对SiCP/Al复合材料进行了车削试验,研究了切削参数对硬质合金YG6刀具磨损的影响规律,并在同等条件下与聚晶金刚石(PCD)刀具进行了对比。发现超声切削的刀具磨损量要小于普通切削的刀具磨损量;超声切削时PCD刀具的磨损量约为YG6刀具磨损量的1/10,这点和普通切削十分相似。     

Environmentally conscious hard turning of cemented carbide materials on the basis of micro-cutting in SEM (2nd report): stress turning with three kinds of cutting tools

Environmentally conscious hard turning and technology have placed increasing importance on the machining process. Cutting fluids have a significant impact on the environment, thus numerous research works are being performed to minimize their use. However, tool wear is very severe in hard turning cemented carbides without the use of cutting fluids. In this research, the effects of dry and wet cutting methods (vegetable oil mist and mineral oil) and tool material on cutting resistance and wear characteristics of cutting tools were experimentally investigated to study the possibility of creating an environmentally conscious hard turning of cemented carbides. Mist and wet cutting of the cemented carbides using poly-crystalline diamond (PCD) cutting tools were adopted to investigate how tool wear on the basis of micro-cutting in the Scanning Electron Microscope (SEM) can be reduced. Additionally, the poly-crystalline cubic boron nitride (PcBN) and the usual cBN cutting tools were compared with the PCD cutting tools. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Dae-Eun Kim HEO Sung Jung was born in Busan, R. O. K., in 1958. He received the Ph.D. in Mechanical Engineering from Osaka University, Osaka, Japan. He is a Full Professor of Mechanical Engineering at Doowon Technical College, Ansong -si, Gyonggi-do, Republic of Korea. His current research interests are in the areas of cutting of difficult-to-cut materials, environmentally conscious machining and cutting tool design.