Tool Wear Characteristics Research Articles

Experimental investigation of tool wear characteristics and analytical prediction of tool life using a modified tool wear rate model while machining 90 tungsten heavy alloys

Tungsten heavy alloys are widely used in the manufacturing of weights for aircraft, missiles, boats and race cars; penetrators; radiation shielding; and radioisotope containers. Manufacturing these components needs machining as a secondary operation. Since tungsten heavy alloys are difficult to machine, the in-depth analysis of tool wear growth and mechanism during machining of these alloys becomes essential. Hence, this work focuses on the experimental study of flank wear growth and its effect on other machining outputs for two different tool geometries (−5° and 2° rake angles) during turning of 90 tungsten heavy alloys. The predominant wear mechanism was identified as adhesion based on scanning electron microscopic analysis. Finally, three commonly used analytical tool wear rate models and one newly proposed model (modified Zhao model) were utilized for the prediction of flank wear growth and tool life. It was observed that the modified Zhao model could predict tool flank wear fairly well within error percentage of 4%–7% and thus could be used as a benchmark while machining difficult-to-cut alloys.

Tool wear characteristics in machining of hypereutectic Al-Si alloys by cemented carbide tool

Tool wear characteristics in machining of hypereutectic Al-Si alloys by cemented carbide tool

Vibration, tool wear and surface roughness characteristics in turning of Inconel 718 alloy with ceramic insert under LN2 machining

Liquid nitrogen (LN2) machining is considered as a safe, clean, and environmentally friendly machining process. This paper aims to investigate the vibration, tool wear and surface roughness mechanism of the ceramic insert during turning of Inconel 718 alloy under dry machining and LN2 machining. The experiments were performed at three cutting speeds (100, 150, 200 m/min), feed rates (0.04, 0.08, 0.12 mm/rev) and depths of cut (0.2, 0.4, 0.6 mm). The experiment results show better machinability and longer tool life in LN2 machining. The vibration acceleration is reduced by 14–32%. A 17–34% reduction of workpiece surface roughness is observed. Flank wear and notch are the predominant wear forms both in LN2 machining and dry machining, and 16–34% reduction of flank wear is noted in LN2 machining.

Performance analysis of coated carbide tool in turning of Nimonic 80A superalloy under different cutting environments

Nimonic 80A is a difficult-to-machine nickel-based superalloy thanks to its superior tensile strength in high temperatures and oxidation resistance. However, cutting fluids applied to improve machinability performance during the processing of such materials increase tool life, while at the same time increasing machining costs and causing health and environmental problems. Thus, the present research has been focused on cutting tool life and wear characteristics and analysis of machined surface in turning of Nimonic 80A superalloy under different cutting environments namely dry, air-cooling and oil-spraying method. The performance of the coated tool has been characterized by using optical microscope, SEM and EDS analysis. The results of the tool life and microscopic analysis showed that the oil-spraying method has longer tool life than dry and air-cooling method in turning of Nimonic 80A alloy. Moreover, the volume of material removed has been modeled by response surface method for predicting tool performance under various machining conditions. Lastly, the microstructural and microhardness variations of the machined surface have been evaluated when the cutting tool reaching the wear criterion. The best performance in terms of tool life and surface integrity was obtained at cutting speed of 60 m/min in oil-spraying environment.

Optimization of Cutting Parameters for MRR, Tool Wear and Surface Roughness Characteristics in Machining ADC12 Piston Alloy Using DOE

Optimization of Cutting Parameters for MRR, Tool Wear and Surface Roughness Characteristics in Machining ADC12 Piston Alloy Using DOE

Fractal Characteristics of Chip Morphology and Tool Wear in High-Speed Turning of Iron-Based Super Alloy.

Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based super alloy, calculate the fractal dimensions of chip morphology and tool wear morphology, and use fractals to analyze their change trend. Meanwhile, a new cutting tool with a super ZX coating is used for a high-speed dry turning experiment. The results indicate that the morphology of the chip is saw-tooth, and its color changes gradually, due to the oxidation reaction. The main wear mechanisms of the tool involve abrasive wear, adhesive wear, oxidation wear, coating spalling, microcracking and chipping. The fractal dimension of the tool wear surface and chip is increased with the improvement of cutting speed. This work investigates the fractal characteristics of chip morphology and tool wear morphology. The fractal dimension changes regularly with the change of tool wear, which plays an important role in predicting this tool wear. It is also provides some guidance for the efficient processing of an iron-based super alloy.

A Novel Technique to Assess the Effect of Machining and Subsurface Microstructure on the Fatigue Performance of Ti-6Al-2Sn-4Zr-6Mo

Aerospace titanium components are manufactured under the strictest standards in order to ensure the highest quality. To develop highly efficient machining processes, extensive research and investment is necessary. For the specific case of rotating titanium critical components, large quantities of forged workpieces are machined to determine the effects of the different machining parameters on tool wear characteristics and component structural integrity and performance. However, testing the different permutations of metal removal parameters and tool combinations is expensive and time consuming at the development stage. The novel approach developed and presented here, enables the machining of smaller titanium parts that can be compared 1-to-1 to parts extracted from industrial machined disc components. This approach not only reduces cost, but ultimately accelerates the research and development process due to more rapid feedback between different iterations of the machining parameters. The proposed technique specifically replicates the face turning operation performed in rotational critical titanium components, such as compressor discs, using small coupons machined in a standard CNC machining centre. The machined coupons can be fatigue tested through a 4-point bending and microstructural analysis can be performed on the tested coupons to directly study the effects of the machining process on the surface and underlying microstructure.

Milling Tool Wear Prediction Method Based on Deep Learning Under Variable Working Conditions

Tool wear prediction is essential to ensure part quality and machining efficiency. Tool wear is affected by factors such as the material, structure, process, and processing time of the parts. Tool wear under the variable working conditions and the above factors show a complex coupling and timing correlation, which makes it challenging to predict tool wear under variable working conditions. This article aims to resolve this issue. First, we establish a unified representation of working condition factors. The stacked autoencoder (SAE) model adaptively extracts tool wear features from the machining signal. The extracted wear features and respective working conditions then combine into a working condition feature sequence for predicting tool wear. Finally, the advantages of the long short-term memory (LSTM) model to solve memory accumulation effects learn the regular wear pattern of the working condition feature sequence to realize the prediction of the tool wear. An experiment illustrates the effectiveness of the proposed method.

On the analysis of temperatures, surface morphologies and tool wear in drilling CFRP/Ti6Al4V stacks under different cutting sequence strategies

In drilling CFRP/Ti6Al4V stacks, the cutting sequence strategy, which determines the coupling effects of each phase machining, affects significantly the machinability of the sandwiched material as well as the tool wear characteristics. The present paper contributes to a scientific understanding of the effects of different cutting sequence strategies on the drilling performance of multilayer CFRP/Ti6Al4V stacks when using uncoated tungsten carbide and diamond-coated drills. Experimental quantification of the in-situ temperatures during the stack drilling was conducted using the method of infrared thermography camera and the instrumentation of drill bits by embedded thermocouples. Drilling forces, exit burr heights of the titanium holes, surface morphologies of the composite holes and tool wear signatures were analyzed. The results indicate that drilling from titanium to CFRP leads to higher magnitudes of the composite cutting temperatures while it benefits the reduction of the stack thrust forces, the improvement of the composite surface morphologies as well as the decrease of the exit titanium burr heights. Additionally, the coupling effects of drilling temperatures and chip adhesion are the influential factors leading to the disparate effects of the cutting sequence strategy on the drill wear progression. Drilling from titanium to CFRP reduces the drill adhesion and flank wear extents owing to the brushing effects of the composite drilling. The diamond-coated drills are confirmed superior to the uncoated ones in terms of lower drilling temperatures, lower drilling forces, minimal hole surface damage, less tool wear while machining the CFRP/Ti6Al4V stacks.

New observations on wear characteristics of solid Al2O3/Si3N4 ceramic tool in high speed milling of additive manufactured Ti6Al4V

Additive Manufacturing (AM) technologies applied to the titanium alloys have attracted attention from industries in recent years. Despite one of the main goals of AM is the reduction of manufacturing steps, semi-finish/finish machining operations are still required so as to obtain the desired geometrical tolerance and surface features. In this study, the solid end mill was manufactured by Al2O3/Si3N4 (Sialon) ceramic materials and employed in high-speed slot milling of Ti6Al4V alloy fabricated by the Direct Metal Laser Sintering (DMLS) AM technology to study the tool wear characteristics during processing. The Raman spectroscopic method was employed to characterize the molecular structures of Sialon ceramics for the manufacturing of the cutting tool. The morphologies and elemental maps of wear region of the ceramic tool were examined by scanning electron microscope and energy dispersive spectroscopy techniques. The results show that the adhesion wear and diffusion wear are the dominant wear mechanisms, and the chemical stability of Al2O3/Si3N4 (Sialon) ceramics fabricated as the solid ceramic tool to the attack of the atoms from additive manufactured Ti6Al4V is relatively weak under the atmosphere. The difference of thermal expansion coefficients of diffusion layer and tool substrate accelerates the initiation and propagation of thermal cracks formed on the diffusion interface. Moreover, fracturing and crater-like groves near the tool edge were finally formed due to the removal of adhered workpiece material.

Effect of Pick Feed on Machining Characteristic of Up Cutting in the High-Efficient Machining by Small Diameter Radius End Mill

In order to improve efficiency of high speed milling, effects of pick feeds of up cutting and down cutting on tool wear and processing characteristics were investigated after cutting pre-hardened steel NAK 55 by TiAlN-coated carbide radius end mill. Flank wear of the tools after up cutting was less than down cutting when the pick feed was smaller than 0.1 mm, which tendency changed when the pick feed was larger than 0.3 mm.

The role of high-pressure coolant in the wear characteristics of WC-Co tools during the cutting of Ti–6Al–4V

Aeronautic applications have been making use of titanium alloys for decades. Ti–6Al–4V is one of the most commonly applied alloys, and although its mechanical properties warrant its acceptance for many applications, the machinability of this alloy remains a challenge. So far, the most successful technique in facilitating this alloy's machining has been the application of High-Pressure Coolant Supply (HPC) on account of its influence on the tribological aspects of the cutting operation. On that premise, this work employs experimental and computational resources to advance the current understanding of the wear mechanism in terms of the tool-chip contact conditions and establish a correlation between coolant pressure, cutting speed, tool life, cutting forces, and chip formation when machining Ti–6Al–4V with HPC supply. Results showed that HPC plays a role in the reduction of tool-chip temperature profiles and contact stresses, positively impacting tool flank wear, oxidation levels and chip formation, also improving chip breakability.

Responses of pre-crystallized and crystallized zirconia-containing lithium silicate glass ceramics to diamond machining

This paper reports on the responses of pre-crystallized and crystallized zirconia-containing lithium silicate glass ceramics (ZLS) to diamond machining in simulated dental milling and adjusting processes. Machining mechanics, tool wear and tribological characteristics, and surface and subsurface damage were investigated. Machining forces and coefficients of friction were measured using a force sensor and high-speed data acquisition system. Diamond tool wear and debris adhesion, and machining-induced surface and subsurface damage were examined using field emission scanning electron microscopy. The results show that both tangential and normal forces of crystallized ZLS were significantly higher than those of pre-crystallized ZLS (p < 0.05) while these forces for both materials significantly increased with the material removal rate (p < 0.05). Coefficients of friction in machining of crystallized ZLS were significantly higher than those in machining of pre-crystallized ZLS. In spite of the minimum wear of applied diamond tools in machining both materials, more crystallized ZLS debris adhesion on tool surfaces was observed. The principal removal mechanisms in machining of both materials were primary fracture and minor plastic deformation of pre-crystallized and crystallized ZLS. However, there was more severe fracture in machining of pre-crystallized ZLS than in machining of crystallized ZLS. Although machining-induced subsurface edge chipping damage in both materials remarkably increased with the feed rate (p < 0.05), such damage was significantly severer in pre-crystallized ZLS than in crystallized ZLS (p < 0.05). These microstructure-property-processing relations provide practical guidance of process selection for high-quality fabrication of ZLS materials.

Experimental investigation on tool wear characteristics of PVD and CVD coatings during face milling of Ti[sbnd]6242S and Ti-555 titanium alloys

Ti6242S and Ti-555, as two typical titanium alloys, are often used to manufacture high-temperature aeroengine parts and landing gear components, respectively. They have different chemical composition and microstructure, which make them have different mechanical properties, and also affect their machinability. In this paper, face milling experiments were carried out to evaluate the wear performance by using CVD-Ti(C, N) + Al2O3 + TiN, PVD-(Ti, Al)N + TiN coated and uncoated tools. The results show that Ti-555 has the worse machinability than that of Ti6242S. When milling Ti6242S, all tools suffered adhesive wear and diffusion wear; the wear of Ti(C, N) + Al2O3 + TiN coated tool was more serious than that of other tools due to the blunt cutting edge; (Ti, Al)N + TiN coated tool suffered micro chipping and coating peeling with the minimal wear loss. When milling Ti-555, uncoated tool suffered serious chipping, abrasive wear and adhesive wear; Ti(C, N) + Al2O3 + TiN coated tool suffered serious chipping and coating peeling with short tool life; (Ti, Al)N + TiN coated tool suffered coating peeling, adhesive wear and diffusion wear. Overall, (Ti, Al)N + TiN coated tools have the longest tool life and are preferred for face milling of Ti6242S and Ti-555 titanium alloys.

A Feature Extraction Method for the Wear of Milling Tools Based on the Hilbert Marginal Spectrum

The Hilbert–Huang transform (HHT) can adaptively delineate complex non-linear, non-stationary signals when used as the Hilbert–Huang marginal spectrum through empirical mode decomposition (EMD) and the Hilbert transform, to highlight local features of signals. Characterized by high resolution, the Hilbert marginal spectrum has been widely applied in mechanical signal processing and fault diagnosis. In the research, an HHT based on the improved EMD was proposed to analyze the cutting force, vibration acceleration (AC), and acoustic emission (AE) signals during tool wear in the milling process. At first, the collected signals were subjected to range analysis, which revealed that tool wear was closely related to the signals collected during the cutting process. Then, EMD was applied to the signals, followed by variance analysis after calculating the energies of each intrinsic mode function (IMF) component. Afterwards, the IMF components significantly influenced by wear degree, while slightly influenced by the three cutting factors (cutting velocity, feed per tooth, and cutting depth), were selected as IMF sensitive to the degree of wear. The HHT was finally applied to the sensitive IMF components of signals containing major tool wear information, thus obtaining the Hilbert marginal spectra of the signals, which were able to reflect the changes in signal amplitude with frequency. On the basis of the Hilbert marginal spectrum, the method defined the feature energy function which was then used as the eigenvector for predicting tool wear in milling processes. The analysis of signals in four tool wear states indicated that the method can extract salient tool wear features.

Study on Highly Efficient Machining by Small-Diameter Radius End Mill

This study aimed to improve the efficiency of mold processing with high-speed milling and to collect basic data on high-speed milling. In this work, we used a milling machine with maximum cutting speed of 160,000 min-1 and maximum feed speed of 15,000 mm/min along with a small diameter end mill to examine tool wear and machining characteristics when the product of axial depth of cut and pick feed as well as the removal rate were constant. We further compared machining efficiencies for surface and side grinding. The results showed that in high-speed milling, tool wear and surface roughness obtained in face cutting were lesser than that obtained in side cutting; thus, surface grinding was more effective.

Characterization of abrasion- and dissolution-induced tool wear in machining

In the present work, a comparative study is reported on tool wear characteristics induced by machining two distinctively different types of materials: Vanadis 10 tool steel containing large amounts of MC and M7C3 carbides, and 316L austenitic stainless steel which is nearly free of hard abrasive phases. Tool life tests were conducted using cemented tungsten carbide tools (WC-Co), both uncoated and TiCN-Al2O3 coated. The subsequent wear characterization included scanning electron microscopy and electron backscatter diffraction (EBSD). Examination of worn WC-Co substrates and coatings revealed significantly different wear characteristics after machining the two workpiece materials. Predominantly abrasion-induced wear was revealed by micro-fragmented tool constituents as well as sub-micron sized grooves and ridges on tool substrates and coatings when machining the tool steel. Moreover, EBSD analysis indicated that the tool substrates exhibited significant superficial strains caused by localized plastic deformation during sliding contact of the tools with the carbides of the tool steel. In contrast, during machining of the stainless steel using uncoated tools, the predominantly dissolution-induced wear resulted in WC-Co substrates with smooth surfaces and absence of significant strain. The worn coatings showed signs of spalling of micro-fragments which indicated the dominant contribution of adhesive wear when machining stainless steel.

Cryogenic Machining of Titanium Ti-5553 Alloy

Titanium alloy Ti-5Al-5V-3Cr-0.5Fe (Ti-5553) is a new generation of near-beta titanium alloy that is commonly used in the aerospace industry. Machining is one of the manufacturing methods to produce parts that are made of this near-beta alloy. This study presents the machining performance of new generation near-beta alloys, namely, Ti-5553, by focusing on a high-speed cutting process under cryogenic cooling conditions and dry machining. The machining experiments were conducted under a wide range of cutting speeds, including high speeds that used liquid nitrogen (LN2) and carbon dioxide (CO2) as cryogenic coolants. The experimental data on the cutting temperature, tool wear, force components, chip breakability, dimensional accuracy, and surface integrity characteristics are presented and were analyzed to evaluate the machining process of this alloy and resulting surface characteristics. This study shows that cryogenic machining improved the machining performance of the Ti-5553 alloy by substantially reducing the tool wear, cutting temperature, and dimensional deviation of the machined parts. The cryogenic machining also produced shorter chips as compared to dry machining.

Effects of Cutting Speed on Chip Characteristics and Tool Wear Mechanisms During Dry Machining of Inconel 718 Using Uncoated WC Tool

The present work deals with tool wear and chip characteristics during dry machining of Inconel 718 using uncoated WC tool. Chip morphology (macro/micro), phenomenon of flank, and crater wear are studied. Effects of cutting speed on cutting force, chip reduction coefficient, approximate temperature generated at the machining zone, and depth of flank wear are discussed. Different wear mechanisms are identified. Abrasion, adhesion, built-up-edge formation, chipping off, grooving, chip welding, and burning are found responsible toward tool wear. It is observed that surface finish of the machined part degrades with increase in flank wear depth. Residuals of Ni, Cr, Fe (major constituents of Inconel 718) are detected through EDS analysis of the adhered chip over the tool surface. XRD analysis also identifies oxides of Fe and Nb present therein. Dry machining condition thus promotes the oxidation of few elements of work material.

Evaluation of Cutting Tool Wear of Earth Pressure Balance Shield in Granular Soil Based on Laboratory Test

Abstract Cutting tool wear is a critical problem for tunneling in soft ground with the earth pressure balance shield. In this study, a cutting tool tester was developed in the China University of Geosciences in Beijing, and a series of tool wear tests were conducted to investigate the characteristics of tool wear in granular soils. The characteristics of cutting tool wear can be quantitatively assessed through the ratio (M0 − M)/M0 (i.e., tool wear rate, %; M0 and M are the mass of the tested blocks before and after the wear test, respectively). The effects of five important factors, including mineralogy, moisture, soil conditioner, test time, and sand content, on tool wear were considered in various test conditions. According to the primary test results, it is observed that (1) high soil hardness produced significantly higher tool wear than low soil hardness in dry condition; (2) with increasing water content, the tool wear gradually increased to a maximum value and then decreased; (3) the foam conditioner mixed in sandy gravel reduced the tool wear dramatically regardless of the cutting tool material, e.g., cemented carbide and Q235 steel; (4) the tool wear increased with the test time in the dry sand mixture, and their relationship showed a good agreement with a power function; and (5) the tool wear decreased as the sand content increased in dry sand-gravel soil mixtures. The reasons for these phenomena were also explored.