Investigation on diamond tool wear in ultrasonic vibration-assisted turning die steels

This paper presents comprehensive theoretical analyses and experimental investigations for evaluating the ultrasonic vibration-assisted turning (UVAT) of die steels with single-crystal diamond tools. The diamond tool wear was found to rely heavily on the feed rate and the cutting speed while being insensitive to the depth of cut and the tool relief angle under the cutting conditions used in the tests. The tool wear characteristics were further studied based on the observation of wear zone using Raman spectral analysis and energy-dispersive X-ray (EDX) analysis. The detection results of the tool worn topography, the phase transformation and the carbon diffusion of diamond crystals revealed that tool wear mainly occurred on the tool flank face due to the graphitization and the diffusion of the diamond tool. Analytical results of the function mechanisms of the ultrasonic turning indicated that the friction force between the tool flank face and the machined surface, which depended mainly on the ratio of the cutting speed and the vibration speed, could be effectively reduced in ultrasonic turning process. The analytical and experimental results indicated that compared with conventional turning (CT), the cutting performance, in terms of the tool life, was markedly improved by applying ultrasonic vibration to the cutting tool.     

Tool wear mechanisms in axial ultrasonic vibration assisted milling in-situ TiB2/7050Al metal matrix composites

The in-situ TiB₂ particle reinforced aluminum matrix composites are materials that are difficult to machine, owing to hard ceramic particles in the matrix. In the milling process, the polycrystalline diamond (PCD) tools are used for machining these materials instead of carbide cutting tools, which significantly increase the machining cost. In this study, ultrasonic vibration method was applied for milling in-situ TiB₂/7050Al metal matrix composites using a TiAlN coated carbide end milling tool. To completely understand the tool wear mechanism in ultrasonic-vibration assisted milling (UAM), the relative motion of the cutting tool and interaction of workpiecetool-chip contact interface was analyzed in detail. Additionally, a comparative experimental study with and without ultrasonic vibration was carried out to investigate the influences of ultrasonic vibration and cutting parameters on the cutting force, tool life and tool wear mechanism. The results show that the motion of the cutting tool relative to the chip changes periodically in the helical direction and the separation of tool and chip occurs in the transverse direction in one vibration period, in ultrasonic vibration assisted cutting. Large instantaneous acceleration can be obtained in axial ultrasonic vibration milling. The cutting force in axial direction is significantly reduced by 42%-57%, 40%-57% and 44%-54%, at different cutting speeds, feed rates and cutting depths, respectively, compared with that in conventional milling. Additionally, the tool life is prolonged approximately 2-5 times when the ultrasonic vibration method is applied. The tool wear pattern microcracks are only found in UAM. These might be of great importance for future research in order to understand the cutting mechanisms in UAM of in-situ TiB₂/7050Al metal matrix composites.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00294-2     

Effect of machining parameters on turning of VAT32® superalloy with ceramic tool

The objective of this research was to study the machining of superalloy VAT32® using alumina-based ceramic tool without cutting fluid, applying different machining parameters to evaluate the surface finish of parts, vibration and main wear of tools. For this, a turning process with a linear trajectory of 30 mm was performed, in which were collected data vibration and surface roughness of the stretch, as well as wear and damage in the tools. The turning tests were performed utilizing cutting speeds of 270, 280 and 300 m/min, a feed of 0.10, 0.18 and 0.25 m/rev and a cutting depth of 0.50 mm. With results, it was identified that the feed influenced significantly both the vibration and the system, since the cutting speed influenced only the vibration. Being that the best results happened for the smaller feed and greater cutting speed. It concludes that the machining of superalloy VAT32® with ceramic tool introduced herself promising.     

基于CVD厚膜金刚石刀具的超声振动切削模具钢实验

采用化学气相沉积（chemicalvapordeposition,CVD）厚膜金刚石刀具进行模具钢超声振动切削实验．首先阐述刀具的材质特点,观测其刀尖微观形貌和切削刃截面轮廓．然后搭建了适应精密／超精密加工需求的超声振动切削实验装置,其中激振机构可稳定实现频率42．0kHz、振幅峰峰值8～9μm的振动输出．通过切削无氧铜实验证明该超声振动切削装置工作有效、稳定后,选用AISI420模具钢进行切削实验,研究切削工艺条件及切削用量对加工质量的影响,得到适用于CVD厚膜金刚石刀具的切削用量选取范围,对比研究发现超声振动切削在提升加工表面质量、减少金刚石刀具磨损方面均优于常规切削．本研究可使切削模具钢时的金刚石刀具磨损VBmax由500～600μm减少至40μm,模具铜表面粗糙度Ra由0．93μm改善至0．09μm．本研究为金刚石刀具超声振动切削模具钢的实用化积累工艺经验,并探索提供可行的技术实现途径．     

Machining of high performance workpiece materials with CBN coated cutting tools

The machining of high performance workpiece materials requires significantly harder cutting materials. In hard machining, the early tool wear occurs due to high process forces and temperatures. The hardest known material is the diamond, but steel materials cannot be machined with diamond tools because of the reactivity of iron with carbon. Cubic boron nitride (cBN) is the second hardest of all known materials. The supply of such PcBN indexable inserts, which are only geometrically simple and available, requires several work procedures and is cost-intensive. The development of a cBN coating for cutting tools, combine the advantages of a thin film system and of cBN. Flexible cemented carbide tools, in respect to the geometry can be coated. The cBN films with a thickness of up to 2 µm on cemented carbide substrates show excellent mechanical and physical properties. This paper describes the results of the machining of various workpiece materials in turning and milling operations regarding the tool life, resultant cutting force components and workpiece surface roughness. In turning tests of Inconel 718 and milling tests of chrome steel the high potential of cBN coatings for dry machining was proven. The results of the experiments were compared with common used tool coatings for the hard machining. Additionally, the wear mechanisms adhesion, abrasion, surface fatigue and tribo-oxidation were researched in model wear experiments.     

铝基碳化硅精密铣削刀具磨损实验研究

针对铝基碳化硅切削加工中刀具易磨损、寿命低、切削难度大和加工成本高等问题,选用不同材料的硬质合金铣刀及金刚石铣刀进行切削加工实验,并利用扫描电镜和工具显微镜对高体积分数铝基碳化硅铣削时刀具磨损形态进行了分析研究.研究表明:硬质合金刀具前刀面和刃口磨损主要形式为粘结磨损和微崩刃,后刀面磨损主要为刻划磨损,而金刚石铣刀加工时刀具磨损很小;YG6X铣刀材料微观组织致密,抗磨损能力较强,宜粗加工时选用;金刚石刀体的硬度远大于SiC颗粒,且金刚石与工件的摩擦系数小,金刚石铣刀寿命远大于硬质合金铣刀,宜精加工时选用.     

EFFECT OF TOOL WEAR AND TOOL SETTING ON PROFILE ACCURACY OF DIAMOND-TURNED NONFERROUS COMPONENTS

Diamond turning technology has gained great importance in high-precision optical component fabrication. The quality of machined optical surfaces is mainly affected by the machine tool's accuracy, cutting tool's quality, and dynamic machining effects. This study investigated the effects of cutting tool conditions and tool set-up error on the surface distortion. Controlled cutting tests were performed on a two-axis diamond turning machine. Spherical mirrors with preset tool offset values and tool height values were turned. The relationship among machined form accuracy, tool offset, and tool height was investigated based on experimental and analytical results. The influence of tool wear on machined surface quality was studied. Factors governing uneven wear along the cutting edge in contour machining were analyzed. A spherical surface with a form accuracy better than λ/10 was produced. Methods for minimizing the effect of tool wear are also discussed.     

High-speed turning experiments on metal matrix composites

The hard abrasive ceramic component which increases the mechanical characteristics of metal matrix composites (MMC) causes quick wear and premature tool failure in the machining operations. The aim of the paper is to compare the behaviour of high rake angle carbide tools with their diamond coated versions in high-speed machining of an Al₂O₃Al 6061 MMC. The influence of the cutting parameters, in particular cutting feed and speed, on tool wear and surface finish has been investigated. The higher abrasion resistance of the coatings results in increased tool life performances and different chip formation mechanisms.     

Chemical vapour deposition (CVD) diamond coated tools performance in machining of PEEK composites

This paper presents a study about the chemical vapour deposition (CVD) diamond coated tool performance in machining unreinforced PEEK and composite PEEK CF30 (reinforced with 30% of carbon fibres).

The experimental procedure consisted of turning operations, during which cutting forces and surface roughness obtained in composite workpieces were measured.

The obtained results showed a best cutting performance for CVD diamond coated tool in machining PEEK composites, particularly in terms of cutting forces and power consumption, when compared with polycrystalline diamond (PCD) and cemented carbide (K10) cutting tools. This fact is very important due to the minor production costs of CVD diamond coated tools in comparison with PCD tools.     

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.     

Experimental Study of Surface Roughness and Tool Flank Wear during Hybrid Milling

Two advanced machining methods such as thermally enhanced machining and ultrasonic-assisted machining are recently considered in many studies. In this article, a new hybrid milling process is presented by gathering the characteristics of these two methods. In order to determine the axial depth of cut and engagement in the process, three-dimensional thermal finite-element analysis is applied to determine the dimensions of softened materials. Finite-element modal analysis is used to determine the dimensions and clamping state of the workpiece while cutting area has the highest vibration amplitude. Full factorial experimental design is applied to investigate the effect of hybrid machining parameters on the surface roughness and tool wear. Tool flank wear was investigated under the condition of constant cutting speed during different period of times. Hybrid milling process with an amplitude of 6 µm and a temperature of 900°C creates a surface with 42% lower roughness in comparison to conventional milling in feed 0.08 mm/tooth. In a study of tool flank wear, the results show that application of TEUAM decreases flank wear at least 16% in comparison to all other processes.     

Effect of cryogenic minimum quantity lubrication on machinability of diamond tool in ultraprecision turning of 3Cr2NiMo steel

This work presents a series of experimental investigations and corresponding theoretical analyses to research on the effect of cryogenic minimum quantity lubrication (MQL) on machinability of diamond tool in ultraprecision turning of typical die steel. The tool wear and machined surface quality were determined as experimental indexes, which were measured using the scanning electron microscope and surface profiler, respectively. Besides, the maximum temperatures of diamond tool surfaces acquired by infrared thermal imager were used to indirectly evaluate the cutting process. The experimental results revealed that cryogenic MQL had obvious advantages in improving diamond tool durability and machined surface quality by comparison with flood cooling, cryogenic gas cooling, and MQL, and its essential function mechanisms were thoroughly understood. On the basis of this, carbon nanofluid was found to achieve optimal tool life in diamond turning compared with polyethylene glycol, castor oil, synthetic ester, and emulsified liquid. Ultimately, the combined machining method of ultrasonic vibration-assisted turning and cryogenic minimal quantity lubrication was proposed in this work. The results showed that this technique could observably improve the machinability of diamond tool and also provide a new direction for exploring a suitable processing method for ultraprecision machining of ferrous materials.     

Comparative study of the effect of surface texturing on cutting tool in dry cutting

Recent researches in the field of dry machining have indicated that surface texture has the potential to influence tribological conditions. Researchers have studied the application of controlled surface microtextures on cutting tool surfaces to improve machining performance by changing the tribological conditions at the interfaces of tool–chip and tool–work piece. An experiment to study the performance of the microtextured high-speed steel cutting implement within the machining of steel and aluminum samples was performed. Surface textures were introduced using Rockwell hardness tester, Vickers hardness tester, and by scratching with diamond dresser on the face of single point cutting tool. Machining in dry conditions was applied on mild steel (EN3B) and aluminum (AA 6351) samples using lathe machine with microtextured and traditional cutting tool for the constant range of feed, depth of cut, and for varying range of cutting speeds. Measurement of cutting force, cutting temperature, and surface roughness of the work surfaces after machining were made. The results showed reduction in cutting forces and cutting temperature with textured tools in comparison with those of the untextured tool. Chips collected from different samples were studied under a microscope and the results showed that textures created on the tool surface by various methods exhibited variations in chip formation. Cutting tools without texture and with texture were comparatively studied and the outcomes of the experimental study are presented in this paper.     

金刚石刀具刃口的动态微观机械强度各向异性评价方法

为了评价金刚石刀具刃口动态微观机械强度的各向异性,对金刚石晶体的动态微观机械强度进行了理论建模,包括抗拉、剪切和抗压强度.通过比较分析动态微观机械强度的各向异性分布特征,提出了基于金刚石晶体动态微观抗拉强度的刀具刃口微观机械强度各向异性评价新方法,即刀具刃口强度评价因子.刀具刃口强度评价因子越高,其对应的刀具刃磨质量或刀具耐用度就越好.最后,分别采用刃磨工艺实验和刀具耐用度实验对刃口强度评价因子的评价适用性进行了验证,实验数据和理论分析结果具有很好的一致性.     

Studies on Machining Parameters While Milling Particle Reinforced Hybrid (Al6061/Al2O3/Gr) MMC

In this article, response surface methodology has been used for finding the optimal machining parameters values for cutting force, surface roughness, and tool wear while milling aluminum hybrid composites. In order to perform the experiment, various machining parameters such as feed, cutting speed, depth of cut, and weight (wt) fraction of alumina (Al₂O₃) were planned based on face-centered, central composite design. Stir casting method is used to fabricate the composites with various wt fractions (5%, 10%, and 15%) of Al₂O₃. The multiple regression analysis is used to develop mathematical models, and the models are tested using analysis of variance (ANOVA). Evaluation on the effects and interactions of the machining parameters on the cutting force, surface roughness, and tool wear was carried out using ANOVA. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. The optimum machining parameters obtained from the experimental results showed that lower cutting force, surface roughness, and tool wear can be obtained by employing the combination of higher cutting speed, low feed, lower depth of cut, and higher wt fraction of alumina when face milling hybrid composites using polycrystalline diamond insert.     

Diamond and cBN hybrid and nanomodified cutting tools with enhanced performance: Development,testing and modelling

The potential of enhancement of superhard steel and cast iron cutting tool performance on the basis of microstuctural modifications of the tool materials is studied. Hybrid machining tools with mixed diamond and cBN grains, as well as machining tool with composite nanomodified metallic binder are developed, and tested experimentally and numerically. It is demonstrated that both combination of diamond and cBN (hybrid structure) and nanomodification of metallic binder (with hexagonal boron nitride/hBN platelets) lead to sufficient improvement of the cast iron machining performance. The superhard tools with 25% of diamond replaced by cBN grains demonstrate 20% increased performance as compared with pure diamond machining tools, and more than two times higher performance as compared with pure cBN tools. Further, cast iron machining efficiency of the wheels modified by hBN particles was 80% more efficient compared to the tool with the original binder. Computational model of hybrid superhard tools is developed, and applied to the analysis of structure-performance relationships of the tools.     

Nano-Scratching resistance of high-chromium white cast iron and its correlation with wear of cBN tool in machining

In this paper, a nano-scratch testing approach was used to measure and evaluate the abrasion wear resistance of high-chromium white cast irons in order to understand the wear mechanism in the interaction between the high-chromium white cast iron and the cBN cutting tool during the machining process. Scratch testing was performed on a nanoindentation instrument using a diamond indenter as the scratch tool. Linear multi-pass scratches in the same path were made on pre-worn surfaces of test materials. The correlation of the scratching resistance and tool wear measured from the machining is presented by the flank wear and maximum scratch depth. The appearance of the cutting edge on a cBN tool suggests that the abrasion wear is mainly related with a combined effect of the carbides and the matrix during machining the high-chromium white cast iron.     

Performance of alumina-based ceramic inserts in high-speed machining of nimonic 80A

The study of machining forces and cutting tool wear during the machining is important for designing and selection of machining system and improving the productivity. This study reports the machinability of Nimonic 80A superalloy with alumina-based ceramic inserts. The objective is to analyze the reason for higher cutting forces generated during machining and tool wear mechanism on machining parameters. The cutting forces and tool wear are found to be mainly influenced by the cutting speed. The main causes of tool failure while machining Nimonic 80A are adhesion and abrasion. The role of tool wear is more dominant on the surface finish at lower cutting speed. Also, with an increase in cutting speed, thermally activated wear quietly increases at tool surfaces. The mechanistic approach is used to model the main cutting force. Developed cutting force model agrees well with experimental cutting force values.     

Effects of high-pressure cooling on the wear patterns on turning inserts used on alloy IN718

Several emerging technologies are being explored to increase the efficiency of machining nickel based alloys. These include the so-called assisted machining processes. Within that group, use of high-pressure cooling has been increasing since its introduction in the 1950s by Pigott and Colwell. The present study compares changes in tool wear patterns for high-pressure cooling (HPC) with those for flood cooling during rough face-turning of wrought nickel-based alloy IN 718. The alloy was face-turned with uncoated carbide tools at a contact cutting speed of 30?m/min, using conventional and high-pressure coolants (HPCs) at 8?MPa (80?bar). Tool wear and cutting force components were recorded. HPC reduced flank wear more than 30%, and reduced cutting forces by more than 10%. In contrast, notch wear is higher and becomes predominant in HPC. Temperatures during turning were also measured and compared to the results obtained from finite element modeling to better understand differences in the notch formation tendency for HPCs compared with conventional.     

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.