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.     

WEAR OF CERAMIC TOOLS WHEN MACHINING CAST IRON

Five commercially available ceramic tool inserts were used for studying the machining characteristics of grey cast iron. These inserts from three suppliers were shown to behave as two groups. The first group containing Al₂0₃ and Al₂0₃/Zr0₂ showed low wear rates over a wide range of cutting speeds and these wear rates were essentially speed independent. This group showed considerable fracture tendency in the speed range 250m/min - 500 m/min. Alumina tools containing TiC/TiN showed higher wear rates which were both speed and TiC content dependant. High TiC content tools demonstrated high wear rates at low speeds and vice versa. TiN appeared to have little, if any, effect on wear rate. The presence of TiC and TiN also appeared to suppress the fracture tendency in the speed range 250m/min - 500 m/min.     

Comparison of tool life and surface characteristics of uncoated,coated carbide and ceramic tools during machining of SiC reinforced ZA43 alloy MMC

Abstract

In the present investigation, machinability issues of zinc–aluminium (ZA43) alloy reinforced with silicon carbide particles (SiC) were evaluated. The fabrication of composite was done through liquid metallurgy technique. Metal matrix composite (MMC) was subjected to turning using conventional lathe with three grades of cutting tools, namely, uncoated carbide tool, coated carbide tool and ceramic tool. Surface roughness and tool wear were measured during the machining process. Results reveal that roughness increases with increase in the reinforcement concentration and particle size. Feed has direct influence on roughness, i.e. surface deteriorates with higher feeds. Depth of cut has very minimum effect on the surface roughness, while inverse effect of cutting speed on the roughness was observed (i.e. increase in the cutting speed leads to better finish on the specimen). Tool wear was studied during the investigation, and it was noticed that MMC with higher reinforcement concentration and particle size cause severe wear on the flank of the cutting tool. Increase in the cutting speed, feed and depth of cut also increases the flank wear on the tool. Out of all the three grades of tools, coated carbide tool outperformed uncoated carbide and ceramic tools.     

Effects of geometric angle and cutting speed on cutting forces and tool wear of ceramic cutting tools during peripheral up-milling of high-density fiberboard

In this paper, cutting forces and tool wear of ceramic cutting tools are investigated by up-milling high-density fiberboard under different geometric angles and cutting speeds. The results show that tangential force (F_t) and normal force (F_r) decrease with the increase of rake angle. The values of F_t and F_r at the higher speed cutting condition are lower than that at the lower speed condition. The flank wear (VB) declines with increased clearance angle and decreased cutting speed. The tool wear patterns observed on the ceramic cutting tools are pull-out of grain, cracking, tipping, and flanking. Abrasive wear and adhesive wear are the main mechanisms of the ceramic cutting tools. In all, on the premise of guaranteeing the ceramic cutting tools’ strength, the ceramic cutting tool with a bigger rake angle and clearance angle is advisable in high-density fiberboard machining, in terms of lowering the energy consumption and production cost required for machining.     

The influence of lubrication on tribological properties of Si3iNi4/1045 steel sliding pairs

Compared with cermet cutting tools, ceramic cutting tools have much better thermal stability and higher hardness. Si₃N4-based composite ceramics have been used progressively more for machining cast iron at very high speed. However, they have been found to be unsuitable for machining steel. One of the factors influencing this difference in behaviour is thought to be serious chemical wear of the ceramic at the high temperatures reached at the cutting tools. Lubrication could reduce the friction and the high temperature of the cutting tool/workpiece contact zone. A simulation test was carried out on a pin-on-disc tribometer in order to investigate the effect of lubrication on the friction and wear of Si₃N₄/1045 steel sliding pairs; the effects of load and speed on friction and wear were also investigated. The results show that suitable lubrication could greatly reduce the friction coefficient and wear rate of Si₃N₄ ceramic. Scanning electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy were used for examinations of the worn surfaces. A wear mechanism of the Si₃N₄ ceramic in sliding contact with 1045 steel is proposed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Drehen und Fräsen pulvermetallurgischer Hartlegierungen für warmgehende Werkzeuge

Turning and Milling of Powder Metallurgical Hard Alloys for Tools in Hot Working Applications Hard metals are high wear resistant materials. The microstructure of these composites consists of hard phases which are embedded in a metal matrix. The high hardness and the high content of the hard phases lead to a difficult machining of these materials. The present study investigates the turning and milling of D3 cold work steel (X210 Cr 12) and the powder metallurgical Fe‐based alloys ASP60 and ASP23 + WC/W₂C. The cutting tool materials were polycrystalline cubic boron nitrides (CBN) and ceramic inserts. The machining process could be judged by means of tool wear and machining quality (surface roughness and changes in the surface near zone). The investigations illustrate that the machinability of the different hard metals depends on the cutting speed and the cutting tool material.     

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.     

Study of deformation zone effects of low,conventional, high and very high speed machining

The paper deals with cutting speed in range 3 m?min^‐1 up to 2200 m?min^‐1 and its complex impact mainly on chip macroscopic shape, chip microstructure, chip compression, tool wear, tool life and machined surface quality and interprets and compares the effects regarding low, conventional, high and very high speed machining based on the dry turning of carbon steel by sintered carbide coated by titanium nitride and ceramic cutting inserts. The deformation zone response for different cutting speeds at the tool‐chip‐workpiece interfaces and their effect on tool wear were studied. The extensive (so called complete) experiments within wide range of values and large number of measurements were carried out. The formation of secondary chip occurring in high speed turning is reported. Moreover, the paper analyses the total machining time involving tool replacement time in terms of high speed machining regarding the obtained experimental results.     

Effect of cutting speed on the performance of Al2O3 based ceramic tools in turning nodular cast iron

This paper presents the results of an experimental investigation on the effect of cutting speed in turning nodular cast iron with alumina (Al₂O₃) based ceramic tools. Three different alumina based ceramic cutting tools were used, namely TiN coated Al₂O₃ + TiCN mixed ceramic, SiC whisker reinforced Al₂O₃ and uncoated Al₂O₃ + TiCN mixed ceramic tool. Turning experiments were carried out at four different cutting speeds, which were 300, 450, 600 and 750 m/min. Depth of cut and feed rate were kept constant at 1 mm and 0.1 mm/rev, respectively, throughout the experiments. Tool performance was evaluated with respect to tool wear, surface finish produced and cutting forces generated during turning. Uncoated Al₂O₃ + TiCN mixed ceramic was the worst performing tool with respect to tool wear and was the best with respect to surface finish. SiC whisker reinforced Al₂O₃ exhibited the worst performance with respect to cutting forces. If tool wear, surface finish and cutting force results are considered together, among the three tools studied, TiN coated Al₂O₃ + TiCN mixed ceramic tool is the most suitable one for turning nodular cast iron, especially at high cutting speeds (V_c > 600 m/min).     

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.     

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。     

基于切削可靠性的新型陶瓷刀具材料的研制

建立了切削可靠性和刀具力学性能之间的关系模型,根据切削可靠性和断裂韧性的要求设计并制备出了颗粒和晶须协同增韧的陶瓷刀具JX-2,其力学性能与晶须增韧陶瓷刀具(JX-1)相当,但成本低,且抗扩散磨损的能力强.将JX-2、JX-1和硬质合金刀具YG6X进行对比切削电铸纯镍实验,JX-2的切削速度最高,磨损寿命最长,其抗磨损能力最强,是加工纯镍或高镍合金等材料的理想刀具.     

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.     

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.     

Cutting performance and failure mechanisms of a pure WC cutting tool in dry cutting of Cr12Mn5Ni4Mo3Al stainless steels and HT200 grey cast iron

A pure WC cutting tool material was fabricated by hot pressed sintering and treated by hot isostatic pressing (HIP). The cutting performance, failure modes and mechanisms of the pure WC cutting tools were investigated via dry cutting Cr12Mn5Ni4Mo3Al stainless steels and HT200 grey cast iron in comparison with those of YW2 cemented carbide tools. General view of the worn tool face was observed by light optical microscopy. Worn and fractured surfaces of the cutting tools were observed by scanning electron microscopy (SEM) and chemical analysis by energy-dispersive X-ray spectroscopy (EDS). The results of cutting process revealed that the wear mechanisms and failure modes of the pure WC cutting tool in cutting various workpiece materials were totally different due to the discrepant adhesion tendency of the workpiece materials to the pure WC material. The different wear behaviors of the pure WC cutting tools in cutting Cr12Mn5Ni4Mo3Al stainless steels and HT200 grey cast iron result in the completely opposite cutting performance and tool life.     

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     

Investigation on Some Machinability Aspects of Inconel 825 During Dry Turning

In the current study, attempt has been made to investigate the influence of cutting speed (Vc) (51, 84, and 124 m/min) on various machining characteristics like chip morphology, chip thickness ratio, tool wear, surface, and sub-surface integrity during dry turning of Inconel 825. Comparable study was carried out using uncoated and commercially available chemical vapor deposition multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) cemented carbide (ISO P30 grade) insert. Chip morphology consists of chip forms obtained at different cutting conditions. Serrated chips were observed when machining Inconel 825 with both types of tool with more serration in case of uncoated insert. The chip thickness ratio increased as cutting speed was increased. Use of multilayer coated tool also resulted in increase in chip thickness ratio. Rake and flank surfaces were examined with scanning electron microscope and optical microscope. Abrasion, adhesion, and diffusion wears were found to be dominating tool wear mechanism during dry machining of Inconel 825. The beneficial effect of coated tool over its uncoated counterpart was most prominent during machining at high cutting speed (Vc = 124 m/min). The surface and sub-surface integrity obtained with coated tool were superior to that while machining Inconel 825 with uncoated tool.     

Machining studies on coated high speed steel tools

This paper reports studies on the machining of type 4340 steel heat treated to Rc 33 by high speed steel tools (type M 42) coated with TiC using the activated reactive evaporation process. The coated tools exhibited a tool life of 300–800% higher than the uncoated tools under continuous cutting conditions. The principal failure mode was flank wear. The cutting forces were measured and were found to be 50% lower for coated tools than for uncoated tools.     

基于PVD-TiN和TiSiN涂层的Al2O3/TiCN陶瓷刀具及其切削性能研究

采用物理气相沉积(Physical vapor deposition, PVD)工艺在Al₂O₃/TiCN陶瓷刀具表面分别沉积了TiN和TiSiN涂层。通过扫描电子显微镜(SEM)观察涂层微观结构, 采用显微硬度计和划痕仪分别表征涂层硬度和测量涂层与基体的结合强度。通过对涂层刀具进行连续干切削灰铸铁实验, 研究TiN和TiSiN涂层对刀具磨损特征的影响并探讨其磨损机理, 同时研究了涂层对工件加工表面质量的影响。结果表明: PVD涂层可显著提高Al₂O₃/TiCN陶瓷的刀具硬度。TiN涂层和TiSiN涂层可分别提高刀具表面硬度25%和65%, 从而增加刀具耐磨性。两种涂层刀具在连续切削灰铸铁实验中主要的失效机理均是挤压变形下的磨粒磨损, 其中TiN涂层刀具还伴随有粘结磨损; 刀具上的PVD-TiN和TiSiN涂层可以有效保护Al₂O₃/TiCN陶瓷刀具基体, 防止崩刃, 进而改善工件表面加工质量。     

Machinability of Zirconia Ceramics in Ultrasonic Drilling

Zirconia is a typical hard and brittle ceramic material, while its fracture toughness is several times higher than alumina. The use of this advanced ceramic is growing. Machining is often required for quality control of the ceramic component. However, extremely high hardness causes serious problems in conventional machining. Nontraditional ultrasonic machining offers an advantageous alternative. The present work investigates the machinability of zirconia ceramics using ultrasonic drilling. The material removal rate, hole clearance, surface roughness, and tool wear are studied by varying static load and amplitude. The material is removed at several cubic millimeters per minute with 0.5 micrometers average surface roughness. Optimal machining conditions was established with the above performance indices.