Wear characteristics of cemented carbide tool in dry-machining Ti-6Al-4V

In machining titanium alloys, due to the low thermal conductivity and high chemical activity of titanium alloys, tool wear is serious and processing efficiency is very low. To avoid the effects of impurities, which were brought by the cutting fluid, the uncoated cemented carbide tool (WC-Co), which was suitable for cutting titanium alloys, was used for the experiments of dry-turning titanium alloy Ti-6Al-4V. A scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometer (EDS) was used to analyze tool wear mechanism. Based on analyzing the friction characteristic of tool–chip interface, tool wear mechanism was also studied and a physical evolution model of tool wear was established. The results showed that there existed serious adhesion, diffusion and oxidation at tool–chip interface and increasing cutting speed accelerated their occurrence. The physical evolution of tool wear behavior can reflect the loss process of tool material very well.     

脉冲磁场处理改善硬质合金与钛合金摩擦行为研究

为了改善硬质合金刀具切削加工钛合金的摩擦磨损性能，从而减少钛合金加工中浓缩乳化切削液的用量，利用脉冲磁场对WC-6Co硬质合金进行强化处理，在不同配比切削液润滑下研究磁场处理对WC-6Co/钛合金的摩擦行为的影响。结果表明：磁场处理大幅提高了WC-6Co/钛合金的摩擦性能，且随着浓缩乳化切削液与水配比的降低，摩擦因数明显降低；脉冲磁场处理后，WC-6Co硬质合金/钛合金摩擦后的表面得到强化，黏结相Co的脱落减少。磁场处理后硬质合金磨损性能的改善，是脉冲磁场作用下Co相磁致伸缩对硬质合金的强化效果以及硬质合金剩磁对切削液中油滴吸附的耦合结果。     

细晶粒硬质合金刀具铣削钛合金损坏机理的研究

基于用Y330细晶粒硬质合金刀具高速铣削Ti6Al4V钛合金的试验,分析了刀具的损坏形态和失效机理。结果表明,在给定的切削条件下,刀具的损坏形态以崩刃和灼烧为主,同时伴有表面材料扩散。据此提出了延长刀具寿命、提高加工效率的途径。     

Lathe Turning of Titanium Using Pulsed Laser Deposited, Ultra-Hard Boride Coatings of Carbide Inserts

Despite several years of research and development, titanium machining remains a challenging task that is currently carried out by the use of straight WC/Co and polycrystalline diamond (PCD) tools. Commercially available coated tools tend to react chemically with titanium, while ceramic tools suffer from chipping and notching. Advancements in cutting tools, particularly coated carbides, are needed to reduce tool wear in machining of titanium alloys. In this work, a recently developed, ultra-hard AlMgB₁₄-20%TiB₂ composite material was applied as a coating on WC/6%Co tool inserts by a pulsed laser (excimer) deposition technique. The coating was smooth, continuous, and fairly uniform in thickness. The average coating thickness was 0.7 μm for a deposition rate of 0.08 nm per pulse. Nanoindentation tests revealed that the hardness of the coating was approximately twice that of the WC/6%Co substrate. Dry machining tool wear tests, conducted with a CNC lathe by turning bar stocks of heat-treated Ti-6Al-4V alloy, showed that the coated tools outperformed uncoated tools by about two times in flank and nose wears and performed nearly same as that of the commercially available TiAlN coated tool. Detailed analysis of worn tools revealed that the wear mechanisms are quite different in coated tools and are similar to those observed in PCD tools. Results agree well with the general observation that a stable, strong adherent layer forms at the interface between the tool and the chip and minimizes the dissolution-diffusion wear mechanism.     

TOOL PERFORMANCE AND CHIP CONTROL WHEN MACHINING Ti6A14V AND INCONEL 901 USING HIGH PRESSURE COOLANT SUPPLY

Single point continuous turning tests were carried out on Ti6A14V and Inconel 901 using various geometries of straight grade (K20) cemented carbide inserts using a high pressure coolant jet directed at the tip of the tool where the chip is formed. Trials were also carried out using a conventional coolant supply for comparison. The test results show that improved tool life can be achieved when machining the titanium-base alloy under the high pressure coolant jet while shorter tool life was obtained when machining the nickel-base alloy. The use of high pressure coolant supply during machining generally maintains constant cutting forces and reduces the chip-tool contact length, thus increasing stresses at the tool edge. This behavior tends to accelerate notching that is predominant when machining the Inconel 901 alloy, resulting in shorter tool life. This effect is not obvious when machining Ti6Ai4V where the tools failed mainly due to excessive flank wear. Effective chip control was achieved when machining both materials because of the cyclic fragmentation mechanism of the newly generated chip.     

Cemented carbide and cermet tooling for film-perforating

The tools used to perforate a particular photographic film started to wear at an unacceptable rate when the film base was changed from cellulose triacetate to polyester (PET). A laboratory investigation was initiated to screen candidate tool materials and identify ones with potential for 10 times life improvement over cemented carbide (WC/10% Co).

The screening tests started with abrasion and corrosion tests on various grades of cemented carbide, cermets and selected ceramics. Concurrent production trials indicated that the laboratory corrosion tests were not correlating with production results. To address this problem, a “nibbler” test was developed which simulates perforating and material removal on a punch after 10⁶ perforations (nibbles) became the screening test metric.

It was determined that abrasion tests do not accurately predict tool material behavior when chemicals are present on or in the materials being perforated. Static corrosion tests do not predict tool response under production conditions. The rubbing of the film on the tool surfaces removes protective films and there can be a significant corrosion component in tool erosion. The nibbler simulates real tool conditions because erosion is produced by actual cutting of coated webs. Nibbler tests in this study indicated that alumina/zirconia resisted film erosion better than cemented carbide, even cemented carbide with PVD coatings. The nibbler tests also indicated that leaving recast layers from electrical discharge machining on cemented carbide greatly increases erosion rates. It should be removed.

Production tests conducted since completion of these laboratory studies suggests that nibbler results correlate with production results. Coated cemented carbides are providing 3 times the service life of uncoated cemented carbides as predicted by the nibbler test.     

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。     

WEAR PERFORMANCE OF MULTILAYER-COATED CARBIDE TOOLS

Three multilayer-coated carbides [two trigon-shaped inserts: Ti(C,N)/TiC/Al₂O₃ (T1), Ti(C,N)/ Al₂O₃/TiN (T2) and one 80°-rhomboid shaped insert: TiC/Al₂O₃/TiN (T3)] were used to machine a martensitic stainless steel at various combinations of cutting speed and feed rate without coolant to assess their wear performance. Significant nose wear and chipping/fracture of the cutting edge were the predominant failure modes affecting tool performance at higher speed conditions. Plucking of tool materials was the main rake face wear phenomenon observed on T1 grade insert with alumina as the top-layer coating when machining at the lower speed conditions. Attrition and plastic flow were the main wear mechanisms observed on the ceramic coating layers, with dissolution-diffusion being the probable wear mechanism of the tool grades where tungsten carbide substrate had direct contact with the flowing chip. The fitted statistical wear models revealed T3 grade insert with 80°-rhomboid shape as having the highest speed-feed capability, resulting in the highest material removal rate relative to T1 and T2 grade inserts with trigon shapes.     

Adhesion Wear on Tool Rake and Flank Faces in Dry Cutting of Ti-6Al-4V

Titanium alloys are very chemically reactive and,therefore,have a tendency to weld to the cutting tool during machining.The deterioration in the tool life caused by adhesion is a serious problem when titanium alloys are cut using carbide tools.The chemical reactivity of titanium alloys with carbide tool materials and their consequent welding by adhesion onto the cutting tool during dry cutting leads to excessive chipping,premature tool failure,and poor surface finish.In the present study,dry turning and milling tests were carried out on Ti-6Al-4V alloys with WC?Co carbide tools.The adhesion on the tool rake and flank face was explored,the adhesive joint interface between the workpiece materials and tools were observed.SEM observation showed that adhesion can be observed both on the rake and the flank face,and was more pronounced in rake face than in flank face.There was evidence of element diffusion from the tool rake face to the adhering layer(vice versa) through the adhesive joint interface,which leads to the tool element loss and microstructure change.While the adhering materials at the flank face can be easily separated from the joint interface owing to the lower temperature and less pressure at the flank face,the adhesive wear attack results in an abrasive wear in the flank face.Moreover,adhesion is more notable in turning than in milling.The proposed research provides references for studying the adhesion between the workpiece materials and the tools,the adhesion mechanisms and their effect on the tool wear.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

硬质合金刀具高速车削钛合金的切削性能研究

采用单因素试验法,用未涂层硬质合金刀具和TiAlN涂层硬质合金刀具对Ti-6Al-4V钛合金进行了高速干车削试验,通过对切削过程中切削力、刀具寿命、切削温度以及加工表面粗糙度的分析,得出了两种刀具高速干车削钛合金的切削性能,为钛合金高速切削刀具的设计提供了试验依据。     

Wear behavior of adaptive nano-multilayered AlTiN/MexN PVD coatings during machining of aerospace alloys

Machining of aerospace materials is one of the major challenges of modern manufacturing. Application of nano-multilayered AlTiN/Me_xN PVD coatings (where Me_x is a transition metal of V-VI groups of periodic table) to cemented carbide tooling results in a significant tool life improvement under conditions of cutting hard to machine alloys such as Ni-based Inconel 718 superalloy and Ti-based TiAl6V4 alloy. Microhardness and coefficient of friction of the coatings were measured during this experiment. Investigations of the coated tool life, wear behavior, chip formation (chip type and undersurface morphology) for cutting tools with nano-multilayered PVD coating were also performed. Morphology of worn tools has been studied using SEM and EDX. This study will show that metallurgical design of the nano-multilayered coating should be tailored to its application. To achieve better tool life when machining Inconel 781, adaptive nano-multilayered AlTiN/MoN coating is recommended, whereas a AlTiN/VN coating is better suited to machining TiAl6V4 alloy. A driving force behind selecting these coatings was a noticeably lower coefficient of friction at elevated temperatures.     

FEM analysis in high speed machining of aluminium alloy (Al7075-0) using polycrystalline diamond (PCD) and cemented carbide (K10) cutting tools

The purpose of this paper is to study the thermal and mechanical behaviour in machining of aluminium alloys (Al 7075-0) using PCD (polycrystalline diamond) and K10 (cemented carbide) tools and to make a comparison between the performances of both tools. The study was made using a commercial finite element software. This software has a user friendly interface and can output several results including cutting forces, temperature, pressure, von Mises stress, maximum shear stress, plastic strain, and plastic strain rate which were the objectives of this study. By analysing the simulations, it was concluded that the polycrystalline tool has a superior performance in terms of cutting and feed forces and temperature when compared to the cemented carbide tool.     

EFFECT OF CUTTING SPEED AND SURFACE CHEMISTRY OF CUTTING TOOLS ON THE FORMATION OF BUL OR BUE AND SURFACE QUALITY OF THE GENERATED SURFACE IN DRY TURNING OF AA6005 ALUMINIUM ALLOY

In the present investigation, AA6005 (ISO: AlSiMg) alloy was machined in turning operation with different cutting tools, such as uncoated cemented carbide insert, PVD TiN coated, CVD diamond coated and PCD insert, under dry environment. Effect of cutting speed was studied for each of the cutting tools with regard to the formation of built-up layer (BUL) or built-up edge (BUE). The rake surface of the tools was characterized by optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopic microanalysis. Particular emphasis was given on wear mechanism of PVD TiN coated insert, conventionally used in machining ferrous alloys, during dry turning of AA6005 alloy. It has been observed that increase of cutting speed from 200 m/min to as high as 1000 m/min could not substantially reduce formation of BUL over tool rake surface during dry machining of AA6005 alloy with uncoated or PVD TiN coated cemented carbide inserts. The potential of diamond-based tools in dry machining of aluminium alloy was also studied. Finally, the effect of cutting speed on surface finish of the workpiece machined with different cutting tools was studied during dry turning of AA6005 alloy.     

钛合金零件高速铣削刀具磨损的试验研究

高速铣削钛合金时,由于切削区内的切削温度高,加剧了刀具的磨损。通过对钛合金TC4的高速铣削实验,得出带TiA lN涂层的硬质合金刀具切削钛合金TC4时的刀具磨损的变化规律和刀具耐用度公式。通过对刀具磨损特性的分析,研究结果主要是刀具表面层的粘结相Co在高温下丧失对WC颗粒的结合强度,磨损机理以高温下的粘结层撕裂磨损为主。     

硬质合金孔加工刀具的技术进展

简要介绍了现代制造技术中常用孔加工刀具的种类、硬质合金刀具的材料与制备.以钻头为例,分析了刀具参数、刃磨、刃口钝化技术对切削性能的影响,综述了硬质合金孔加工刀具技术的发展趋势.     

Experimental assessment of textured tools with nano-lubricants in orthogonal cutting of titanium alloy

In this study, we investigated the effects of composite nano-Cu/WS₂ lubricating oil and single-point diamond indentation-textures on improving the cutting performance of YG8 cemented carbide tools, which is crucial for textures tool applications. The aims of the study were to improve wear resistance and reduce chip adhesion at the tool’s rake face in cutting of titanium alloys. Dot textures with different spacings were fabricated on the surface of YG8 cemented carbide tools through the single-point diamond indentation method, and composite nano-Cu/WS₂ lubricating oil was prepared. Orthogonal cutting tests were carried out under dry cutting and minimal quantity lubricated (MQL) conditions. Investigate the effect of different texture spacing on the cutting performance in the light of cutting forces, friction coefficient, the deformed chip thickness, tool adhesions, and chip morphology. The results show that the dot texture effectively improved the lubrication conditions in machining titanium alloys under the MQL conditions. The dot texture is effective at low speed in the dry cutting conditions. With the increase of cutting speed, the friction coefficient of dot texture tool is affected by texture spacing, and the friction coefficient of DT-200 tool is the smallest. In addition, composite nano Cu/WS₂ lubricating oil forms a lubricating film on the wear path by atomizing the lubricating oil and stores it in the dot texture, which enhances the anti-wear performance in the cutting process and reduces the cutting force and friction coefficient at the tool chip interface. By evaluating cutting force, friction coefficient, chip and tool morphology, it is concluded that DT-100 tool is more effective in improving lubrication conditions.

     

高速切削Ti6Al4V钛合金时切削温度的试验研究

应用硬质合金刀具对Ti6Al4V钛合金材料进行了高速车削和高速铣削试验,研究分析了干切削、空气射流及氮气射流条件下的切削温度变化情况。研究结果表明,氮气射流及空气射流条件下的切削温度明显低于干切削条件下的切削温度,而氮气射流条件下的钛合金高速切削温度则略低于空气射流条件下的切削温度。     

Analysis of tool wear patterns in finishing turning of Inconel 718

This paper focuses on the analysis of tool wear mechanisms in finishing turning of Inconel 718, one of the most used Ni alloys, both in wet and dry cutting. Cemented carbides, ceramics and CBN tools are suitable for machining Ni alloys; coated carbide tools are competitive for machining operations of Ni alloys and widely used in industry. Commercial coated carbide tools (multilayer coating TiAl/TiAlN recommended for machining Ni alloys) were studied in this work. The feasibility of two inserts tested for dry cutting of Inconel 718 has been shown in the work. Experimental test were performed in order to analyze wear patterns evolution. It was found great influence of side cutting edge angle in tool wear mode.