Improve Tool Life Research Articles

Turning of Inconel 718 with whisker-reinforced ceramic tools applying vegetable-based cutting fluid mixed with solid lubricants by MQL

The rule of thumb in the machining of nickel base superalloys with ceramic tools is to cut dry and no attempt of applying MQL with the addition of solid lubricant was made, according to the literature consulted. The main objective of this study is to evaluate the effect of the addition of solid lubricant in vegetal base oil applied by MQL (Minimum Quantity of Lubricant), when turning Inconel 718, with whisker-reinforced ceramic cutting tools (Al2O3 + SiCw). Tool life, tool wear mechanisms, surface integrity (microhardness, microstructure and roughness) and cutting force were evaluated. The results showed that the addition of MoS2 substantially improved tool life; types of dominant wear were the notch, flank and small crater, while the main wear mechanisms observed were adhesion and abrasion; cutting fluids improved the surface quality, Ra, and better results were found using vegetal base oil + 20% of graphite; as to the cutting force, the lubricants produced the lowest values.

Influence of parameter matching on performance of high-speed rotary ultrasonic elliptical vibration-assisted machining for side milling of titanium alloys

In this paper, a novel high-speed rotary ultrasonic elliptical vibration-assisted machining method (HRUEM) for side milling is proposed to overcome problems associated with short tool life and low process efficiency during the titanium alloy finishing process. First, a theoretical model of separate-type HRUEM is presented and matching mechanisms and vibration period delay coefficient are fully analyzed. Feasibility experiments were performed used to compare the HRUEM method under different parameter matching conditions for titanium alloy milling with the conventional milling (CM) method. Then, a detailed analysis of process outputs including cutting force, chip formation, tool flank wear, surface topography, and roughness was performed. Based on the analytical model, micro-chips can be achieved with reasonable parameter matching using separate-type HRUEM. The process was further investigated experimentally to determine the tool life. Negative relief angle cutting introduced by HRUEM is found to be crucial and may prevent improvement in tool life. However, tool life of separate-type HRUEM with no negative relief angle cutting can be extended several times compared to CM. In addition, microscope observations of the machined surface revealed more uniform microstructures with HRUEM under reasonable parameter matching cutting conditions.

Comparison machining performance of Al2O3, ZTA and ZTA doped Cr2O3 cutting tools on AISI 1045

This paper presents the comparison of machining performance for cutting tools that fabricated by pure alumina (Al2O3), Zirconia Toughened Alumina (ZTA) and Zirconia Toughened Alumina doped with Cr2O3 (ZTA Doped Cr2O3). Solid-state method was employed to prepare ceramic mixtures starting from 12 h ball milling with 40 rpm rotational speed. The green bodies were formed by 5 ton manual hydraulic press and 300 MPa Cold Isostatic Press (CIP) compaction pressure. The compacted powders then were sintered at 1400 °C and 9 h soaking time in the form of RNGN 120600 designated cutting tools. Properties assessment of the fabricated cutting tools were analysed based on hardness and density. The machining evaluation was performed by turning AISI 1045 with cutting speeds of 150–350 m min−1, feed rate of 0.125 mm/rev and depth of cut of 0.5 mm. The results show that maximum hardness recorded for ZTA Doped Cr2O3 with 13.73 GPa Vickers hardness and 3.82 g cm−3 density, followed by ZTA (12.75 GPa, 3.85 g cm−3) and pure Al2O3 (4.9 GPa, 3.76 g cm−3)In terms of machining performance, ZTA Doped Cr2O3 recorded highest tool life of 330-s with 57% improvement of tool life as compared to ZTA (210-s) and 200% improvement of pure Al2O3 (110-s). Dominant wear mechanisms for the fabricated cutting tool appeared to be notch wear, abrasive wear and chipping at the flank wear area.

Machining performance and tool wear analysis on cryogenic treated insert during end milling of Ti-6Al-4V alloy

The present paper aims to study the machinability of Ti-6Al-4 V alloy with PVD TiAlN/NbN coated tungsten carbide insert under cryogenic treated (i.e 24 h & 48 h) and untreated conditions. The output responses are evaluated in terms of tool wear, surface roughness, chip morphology, cutting force and vibration acceleration signal. The experimental results showed that cryogenic treated insert depicts better machinability and improved tool life when compared to untreated insert under the similar set of working conditions. There was significant reduction in the cutting forces observed during 48 h cryogenic treated insert.

Effect of cutting parameters on tool wear, cutting force and surface roughness in machining of MDN431 alloy using Al and Fe coated tools

Thin solid films are used in cutting tools in order to improve its performance, reduce tool wear and improve tool life. Cathodic arc evaporation is the state of art PVD technique widely accepted in industries for the development of thin solid films. The turning cutting tool inserts are coated with AlCN/AlC and FeCrN monolayer thin solid films using cathodic arc evaporation technique. Quality characteristics of thin films are estimated using Calo and VDI3198 tests. Thickness of the coatings are found to be 1.430 and 1.475 μm for AlCN/AlC and FeCrN coatings respectively and adhesion quality of HF1 is attained. Performance of the thin solid films are evaluated in machining MDN431 steel with range of cutting speed (59–118 m min−1), feed rate (0.062–0.125 mm/rev) and depth of cut (0.2–0.4 mm). Experiments are performed based on full factorial design and regression analysis. Optimization of the process parameters is carried out using combined techniques of desirability and Particle swarm optimisation (PSO). The objective of the study is to establish correlation between machining parameters with cutting force, tool wear and surface roughness. Optimal process parameter for least cutting force and surface roughness are obtained for coatings. ANN has been adopted to improve the coefficient of determination (CoD) and capability of predictive regression models. ANN trained model and mathematical regression models are adequate to predicted the responses, which follows the experimental data with minimum absolute error. The AlCN/AlC coatings exhibited lower cutting forces and surface roughness than FeCrN coated tools. Tool wear was reduced by 3.62 times in AlCN/AlC and 1.63 times in FeCrN coated tools compared to uncoated tool which is due to increased hardness and elastic modulus of the coating.

Experimental evaluation on texture of flank face on tool wear in chamfer milling of stainless steel

This paper presents a novel grinding enabled texture, ‘V’ shaped texture (VST), on flank face. To implement the texture on a cutting performance, a set of chamfering experiments of stainless steel materials used as 3C product shell usually are presented. Cutting forces, surface qualities, and tool wear are measured and compared, of which results show that both smallest surface roughness and longest tool life are achieved by using a 30° VST chamfer tool. By comparing the results, a clear conclusion can be drawn that texture types and angles are not independent factors to cutting performance; therefore, a suitable combination of texture types and texture angles can provide a significant improvement of tool life and surface quality.

Dynamic behaviour of miniature laser textured skis

ABSTRACT Friction between moving bodies in mutual contact is a field studied in depth. A strategy to improve the tribological performance of mechanical components consists of modifying the surface microstructure using the laser surface texturing (LST) technique. For instance, the technique was shown to improve tool life and reduce energy consumption in applications concerning industrial manufacturing and automotive industry. Concerning sports equipment, e.g. skis, these are tribological systems different from generic mechanical components, and as such they require further attention to exploit the benefits of textured surfaces. In this work, LST was applied in the form of microholes (dimples) on two metallic materials, namely AISI 301 and a commercial aluminium alloy (Titanal®), used for ski manufacturing. Geometrical-morphological characteristics of the textured surface and their wettability were investigated. Finally, prototype mini-skis were manufactured and tested under different ambient snow and speed conditions. Results show that LST can reduce the friction coefficient and improve performances.

A Study on the Punch Shape for Improving Tool Life in Shearing AHSS

The adoption of hot rolled AHSS(Advanced High-Strength Steel) has been increased in accordance with the weight reduction of the chassis. The problem of tool life in punching the hole for high-strength steels is more important. Using the high-grade die material is one of the method to improve tool life. Another method for increasing the tool life is reducing the maximum punching load. We investigated the effect of tool shape on reducing the punching load. Conventional, shear-angled and humped tool geometry are considered for punching the flat sheets with 780MPa strength. In flat sheet, the maximum punching load is compared for each case of puch types. Maximum punching load is reduced by 40% of conventional punching process. For investigating the effect of punch shape in a real part, the punching process for the vent hole of the conventional wheel disc is modeled with FEM. The maximum load is efficeintly reduced by using the shear-angled punch.

Performance of cryogenically treated WC drill using tool wear measurements on the cutting edge and hole surface topography when drilling CFRP

Drilling CFRP poses major challenges from the perspective of rapid tool wear and poor hole quality, with the development of higher strength fibers further accentuating these problems. Cryogenic treatment is one way of increasing tool hardness thereby improving tool life and hole quality through longer retention of cutting edge sharpness. In this study, tool wear is monitored by measuring flank wear, cutting edge flatting (CEF), peak flatting (PF) and cutting edge surface roughness (CESR). While flank wear is unable to distinguish the better performance of the cryo-treated drill from the untreated drill, the other wear parameters are able to account for the better hole quality (exit delamination) produced by this drill. CEF and PF are direct measures of the extent of cutting edge blunting unlike flank wear which measures wear along the flank due to rubbing. Fiber pullout is the primary reason for deterioration in surface finish and Rz and Rv are better measures than Ra in estimating surface quality.

A novel treatment for cutting tools for reducing the chipping and improving tool life during machining of Inconel 718

Chipping and high tool wear are considered the most challenging issues associated with machining of superalloys, including Inconel 718. Despite numerous attempts in this area, it is still considered a critical drawback of this class of materials for application in different industries. A new tool treatment technique is proposed for improving the tool wear and reducing the chipping during machining of Inconel 718. The treatment involves less than two seconds of machining on an aluminum-silicon (Al-Si) workpiece prior to the actual machining of Inconel. In this way, the “pre-machining process”, deposited a very thin layer of Al-Si on the tool face. During the subsequent machining of the Inconel bar, the Al-Si was melted due to the high temperatures of Inconel machining. The molten material channeled itself through the microcracks on the tool surface and seized their propagation. The sliding of the tool on the low friction Al-Si layer resulted in much lower forces, less sticking, seizure and built-up edge formation and, thereby, in less tool wear and chipping. Several beneficial lubricious and thermal barrier tribo-films were also formed on the tool face, which further protected the tool from chipping and severe tool wear. Reducing the contact pressure, friction and temperature during machining resulted in considerable reduction in the machining induced work-hardening of the workpiece material, which is considered as one of the most important factors affecting chipping during machining of this class of materials. Moreover, the ductility of Al helped to dampen the vibrations during machining and helped in tool chipping prevention. Finally, the preconditioning of the tool itself through this process resulted in tool performance improvement by lowering the tool wear at the running-in stage. The new method resulted in a significant reduction in tool chipping and an overall improvement in tool life. Considerable improvements in the surface integrity of the machined part were also obtained. The contributing mechanisms are discussed using detailed material characterization techniques.

Experimental and finite element analysis on machining of Ti6Al4V using dual layer coated carbide inserts

There is a want for materials of high hardness and resistance for aerospace applications. Metal cutting of the said kind of blends and metals needs special machining inserts that occasionally is not cost-effective and even unfeasible. In addition, even the untraditional methods are commonly limited to the socket of sight of productivity. The growth of built-up brink and bonding coat on the insert rack surface also worsens on one needle, the profile and effectiveness of machining insert and on the other needle, the surface quality and measurement accurateness of the finished product. The usage of coated tool inserts will diminish the development of brink and bonding coat to a considerable extent which in turn improves tool life thereby reducing tool wear. This paper will focus on studying the effect of machining constraints on machinability of Ti6Al4V using carbide cutting inserts with double layer and without coating in metal cutting without coolant and by examining the stress spreading, turned surface finish and insert attire. Nine experiments using uncoated inserts and dual layer coated inserts were conducted by varying the machining speeds and feeds. The machining process was also simulated in AdvantEDGE Workbench to study corresponding stress and strain distribution.

Residual stress, tensile strength, and macrostructure investigations on ultrasonic assisted friction stir welding of AA 6061-T6

In recent decades, ultrasonic vibrations are used in manufacturing processes because they can improve tool life, material performance, and quality. One of them which can be integrated with ultrasonic vibrations is friction stir welding called ultrasonic assisted friction stir welding. In previous studies, the effect of ultrasonic vibrations on the mechanical, metallurgical, and thermal properties was investigated and there is not any residual stress investigations on ultrasonic assisted friction stir welding. Since residual stress plays an important role in performance and stability of components, the influence of ultrasonic power on the longitudinal residual stress in friction stir welding is investigated in this work. In spite of residual stress, tensile strength and quality of weldment were investigated as complementary terms to ensure successful performance of ultrasonic assisted friction stir welding. The findings indicated that high-frequency vibrations with power of 200 W can reduce the maximum tensile residual stress about 45% and significantly increase tensile strength. Also, ultrasonic vibrations prevent defect such has voids and tunnel in weld zone due to peening effect in ultrasonic assisted friction stir welding.

A new turning system assisted by chip-pulling

This paper presents a new turning system where the guided cut chip during turning is pulled using an external pulling device to attain high-performance cutting. An electro-mechanical pulling device with sensor-less chip tension monitoring function is designed to steadily pull the guided chip and robustly assist the turning operation. The effect of chip tension on the process is modeled and experimentally verified. The developed chip pulling system is utilized to achieve direct real-time control of the cutting process and zero thrust force cutting is demonstrated. Developed system effectively reduces cutting energy for improved tool life and regulates cutting forces for high performance turning.

Nanoparticles of Zn and ZnO as extreme pressure (EP) additives for lubricants

The tribological behavior of moving components and tooling in the automotive industry is a critical issue for improving tool life and increasing efficiency. This work discusses the effects of Zn and ZnO nanoparticle additives homogeneously dispersed within a metal-forming synthetic fluid at various filler fractions: 0.01, 0.05 and 0.10wt.%. Nanolubricants were evaluated under scuffing conditions at extreme pressures (EP) conditions using a four-ball tribotester in order to obtain the load-carrying capacity (poz) behavior, and overall tribological characteristics. This method has shown, with great precision, the influence of the nanofillers on the EP behavior of conventional lubricants. Worn surfaces were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) to determine the tribological mechanisms of nanoparticles. An Alicona 3D surface measuring system was used for measuring the surface roughness of the wear scars. Both nanoparticles exhibited better friction-reducing and anti-wear properties compared to the base synthetic fluid. For Zn-based nanolubricants, an enhancement of ~180% in poz was obtained with 0.10wt.%, showing the effect of the spherical nanostructures that were tribosintered onto the surface due to the EPs of the test. Furthermore, the highest enhancement in poz (up to 250%) was achieved with incorporation of 0.10wt.% of ZnO demonstrating the potential of nanolubricants for improving the efficiency of mechanical components.

Performance assessment of microwave treated WC insert while turning AISI 1040 steel

This study attributed to post treatment of tungsten carbide (WC) inserts using microwave irradiation. Tungsten carbide inserts were subjected to microwave radiation (2.45 GHz) to enhance its performance in terms of reduction in tool wear rate, cutting force surface roughness and improvement in tool life. Performance of tungsten carbide insert is very much affected by machine operating parameters i.e. speed, feed and depth of cut. An attempt has been made to investigate the effects of machining parameters on microwave treated tool inserts. This paper describes the comparative study of machining performance of untreated and microwave treated WC tool inserts used for turning of AISI 1040 steel. Machining performance has been evaluated in terms of flank wear, cutting force, surface roughness, tool wear mechanisms. Critical examinations of tool wear mechanisms and improvements in metallurgical properties such as microstructural change, phase activation of WC grains were identified using scanning electron microscope (SEM). Results obtained from the turning using the microwave treated tool inserts showed a significant reduction tool wear thereby enhancing the surface quality of workpiece.

Through-tool minimum quantity lubrication and effect on machinability

This paper simulated through-tool minimum quantity lubrication (MQL) to characterize micromist droplet size and distribution. The effect of nozzle surface roughness and air pressure was experimentally performed to study the lubricant droplet and its effectiveness in micromilling of Inconel alloy. The external MQL simulated internal flow in commercially available drill with internal cooling channels. Droplets were collected on a glass plate from which the average airborne diameters and standard deviation were calculated. The droplet diameter and distribution were most sensitive when using nozzle with rough internal surface. MQL at different conditions was used in micromilling of Inconel 718 blocks that were additively printed by selective laser melting technique. Micromist generated from a rough nozzle at 550 kPa effectively improved tool life and produced micromilled slots with surface finish Sa of 1.5 μm.

Comparison of machinability of manganese alloyed austempered ductile iron produced using conventional and two step austempering processes

Austempered Ductile Iron (ADI) is a revolutionary material with high strength and hardness combined with optimum ductility and toughness. The discovery of two step austempering process has lead to the superior combination of all the mechanical properties. However, because of the high strength and hardness of ADI, there is a concern regarding its machinability. In the present study, machinability of ADI produced using conventional and two step heat treatment processes is assessed using tool life and the surface roughness. Speed, feed and depth of cut are considered as the machining parameters in the dry turning operation. The machinability results along with the mechanical properties are compared for ADI produced using both conventional and two step austempering processes. The results have shown that two step austempering process has produced better toughness with good hardness and strength without sacrificing ductility. Addition of 0.64 wt% manganese did not cause any detrimental effect on the machinability of ADI, both in conventional and two step processes. Marginal improvement in tool life and surface roughness were observed in two step process compared to that with conventional process.

Electroplastic Drilling of Low- and High-Strength Steels

When postforming machining operations are required on high-strength structural components, tool life becomes a costly issue, often requiring external softening via techniques such as laser assistance for press-hardened steel components. Electrically assisted manufacturing (EAM) uses electricity during material removal processes to reduce cutting loads through thermal softening. This paper evaluates the effect of electric current on a drilling process, termed electroplastic drilling, through the metrics of axial force, and workpiece temperature when machining mild low carbon steel (1008CR steel) and an advanced high strength press hardened steel. A design of experiment (DoE) is conducted on 1008CR steel to determine primary process parameter effects; it is found that electricity can reduce cutting loads at the cost of an increased workpiece temperature. The knowledge generated from the DoE is applied to the advanced high strength steel to evaluate cutting force reduction, process time savings, and tool life improvement at elevated feedrates. It is found that force can be reduced by 50% in high feedrates without observing catastrophic tool failure for up to ten cuts, while tool failure occurs in only a single cut for the no-current condition. Finally, the limitations of the developed model in electroplastic drilling are discussed along with future suggestions for industrialization of the method.

Optimization of EDM Machining Parameters to Machine INCONEL – 825

It is observed that in recent trend INCONEL material has tremendous application in aeronautical, aerospace industry and automobile engineering because of its favorable properties. Therefore “Inconel 825” material has been chosen to machine by EDM. But EDM has a disadvantage of lower MRR. So an experimental investigation has been carried out to study machining parameters of EDM to improve MRR and reducing TWR, surface roughness and kerf width. Here heat treatment process has been studied and applied to improve tool life by reducing tool wear rate. In this experiment Copper tool has modified by changing its grain growth structure by step hardening process and results in both heat treated and without heat treated tools are compared.

Characteristics of ZrC/Ni-UDD coatings for a tungsten carbide cutting tool

This work deals with the features of the structure of combined ZrC/Ni-ultradisperse diamonds (UDD) coating synthesized by electroplating and cathode arc evaporation physical vapor deposition (CAE-PVD) techniques on the tungsten carbide WC – 2 wt% Co on cutting inserts to improve tool life. The microstructure, phase composition, and micro-scratch test analysis of the ZrC/Ni-UDD coating were studied. The ZrC/Ni-UDD coating consists of separate phases of zirconium carbide ZrC, α-Ni, and Ni-UDD phase. The surface morphology of the coating shows a pattern with pits, pores, and particles. Separated nanodiamond particles are present in the pores of the combined coating. Therefore, the structure of the bottom layer of Ni-UDD affects the morphology of the surface of the ZrC/Ni-UDD coating. The obtained value of the critical loads on the scratch track of the coating in 26 N proves a sufficiently high value of the adhesion strength of the intermediate Ni-UDD-layer with hard alloy of WC-Co substrate. Due to their unique structure ZrC/Ni-UDD-coatings can be used to increase the durability period of a wood-cutting milling tool for cutting chipboard by CNC machines.