Dry Machining Performance Research Articles

Comparative study of dry machining performance using hybrid textured cutting insert

ABSTRACT Dry machining is an environmentally friendly process and minimizes machining costs. Also, using cutting fluids in machining affects the operator’s health risks and the surrounding environment. One of the alternatives is surface texture on the coated cutting tool, known as Laser Surface Texturing (LST). In the current research work, Hybrid Textured Tools (HTT) in a combination of dimples and grooves were developed, and the performance of the tools was studied. The experimental findings assert that incorporating HTT during machining operations conclusively leads to a substantial reduction of 47% in the cutting force (Fc), 12% in tool-chip interface temperature (TCT), 26% in surface roughness (Ra), and 30% in flank wear (Vb) in comparison to non-textured tools (NT). HTT implementation can enhance machining performance, improve efficiency, and reduce tool wear, leading to better-quality products.

Study on wear morphology of uncoated and MT-CVD TiCN-Al2O3 coated carbide inserts during dry machining of Inconel 825 superalloy

The adoption of the High Speed Machining (HSM) approach by industries to enhance productivity is crucial in order to fulfill the growing demand of the global market. Understanding superalloys' machining behavior is also necessary since they play a significant role in a variety of industries, including the aerospace industry, marine engine parts, biomedical applications, chemical and petrochemical industries, and nuclear fuel processing plants. Hence, dry machining performance of ‘difficult-to-cut’ aerospace superalloy Inconel 825 is studied herein. With uncoated and MT-CVD TiCN-Al2O3 coated carbide inserts, machining experiments are performed at various cutting speeds. Detailed tool wear mechanisms are discussed for each of the cutting inserts with regard to different cutting speeds and hence the performance gain with coated carbide tools is understood as compared to its uncoated counterpart for dry machining of Inconel 825 superalloy.

Improving dry machining performance of surface modified cutting tools through combined effect of texture and TiN-WS2 coating

In this research work, investigation on different surface modification techniques on cutting tools such as TiN-WS2 coating (T2), textured cutting tool (T3) and TiN-WS2 coated textured tool (T4) in dry machining of Ti-6Al-4V has been carried out and compared with commercial tool (T1). The presence of (002) orientation corresponding WS2 was observed in the diffraction pattern and this in turn was said to provide lubricity properties to the coatings. The cutting force generated during machining was reduced by 14 % for T4 tool when compared to T1. The T4 tool showed an increase in the shear angle by 7.5 % and decrease in coefficient of friction by 47 %. The prime mechanism attributed to the better performance of cutting tool was reduced tool-chip contact length. The T4 tools showed a 13 % reduction in tool-chip contact length when compared to commercial tools. The tool life of the T2, T3 and T4 tools was improved by 35 %, 29 % and 43 % respectively in comparison to commercial tools. The TiN-WS2 coatings, through its effective lubricity properties have said to nullify the effect of coating affinity between the tool and workpiece as evidenced by the absence of built-up edge on the tool rake face while machining using TiN-WS2 coated tool. The combined effect of TiN-WS2 coatings and surface textures have resulted in better machining characteristics, suggesting it as a suitable surface modification for dry machining of Ti-6Al-4V.

Machining performance of TiSiN(Ag) coated tools during dry turning of TiAl6V4 aerospace alloy

One of the main opportunities to increase the tool life during the dry machining of “hard-to-cut” aerospace alloys is the possibility of protecting the components with self-lubricant coatings. Here, self-lubricant TiSiN(Ag) coatings deposited by HiPIMS working in DOMS mode were deposited onto two types of cutting inserts to assess the influence of the solid lubricant (Ag) on the dry machining performance during turning of the TiAl6V4 aerospace alloy. First type of cutting inserts were tested in laboratorial environment using a conventional lathe, whilst, second types of inserts were tested in an industrial automated computer numerical control – CNC machine in an enterprise premises. Tests in the CNC machine were performed to assess their performance benchmarked in relation to a commercial insert coated with AlTiN coating. In both of these tests, the same behaviour was found with the addition of silver clearly displaying an improvement in the tool life of the inserts, especially for higher cutting speeds. Addition of silver also showed its solid lubricant effect by reducing either the wear or the formation of built-up edges (BUE) during the tests and, thus, contributing to an increase in the tools lifetime. Ultimately, this work shows the potential use of TiSiN(Ag) coatings for machining TiAl6V4 aerospace alloy under dry conditions.

Dry Machining Performance of AA7075-T6 Alloy Using Uncoated Carbide and MT-CVD TiCN-Al2O3-Coated Carbide Inserts

The present study examines dry machining performance of AA7075 T6 alloy using uncoated and MT-CVD TiCN–Al2O3-coated carbide inserts. Machining performance is assessed with regard to tangential cutting force, tool tip temperature and depth of flank wear. The performance of coated tool is compared to that of uncoated insert. In addition, different modes of tool wear and chip morphology are studied in detail. It is experienced that coated tool causes lower tool tip temperature and lesser flank wear than untreated counterpart. Apart from abrasion, adhesion and built-up layer formation; attrition wear is distinctly visible in case of uncoated tool. On the contrary, in addition to common wear modes, coated tool also experiences diffusion wear.

Influence of cutting insert (uncoated and coated carbide) on cutting force, tool-tip temperature, and chip morphology during dry machining of Inconel 825

During metal machining, tool material (substrate as well as coating) plays an important role to influence machinability of any work material. Dry machining performance of ‘difficult-to-cut’ aerospace superalloy Inconel 825 is studied herein. Machining experiments are conducted at different cutting speeds using uncoated carbide, and MT-CVD TiCN-Al2O3 coated carbide inserts. Machining performance is assessed in purview of magnitude of cutting force, approximate tool-tip temperature, and quantitative chip morphological parameters. Performance of coated tool is compared to that of uncoated insert. It is estimated that coated tool causes 39.79% reduction in tangential cutting force (at cutting velocity ∼121 m/min) when compared to uncoated counterpart. Higher tool-tip temperature of the coated insert caused higher chip curling. Shear band microhardness of chip (obtained by using coated tool) appear higher than that of uncoated insert.

Dry turning performance of TiN–WSx/TiN hard-lubricious bilayer composite coating

Dry machining is receiving immense attention worldwide to eliminate or minimize the harmful environmental effects of cutting fluids. The present work investigates dry machining performance of a bilayer coating with top-layer of hard-lubricious TiN–WSx, supported by a hard TiN under layer. During dry turning of AISI 1060 steel, the bilayer coated carbide tool registered significantly less cutting forces as compared to its TiN coated counterpart in the cutting velocity range of 77–230 m/min. In prolonged turning test at cutting velocity of 200 m/min, it also exhibited notably higher tool life on the order of 13 and 2.17 times respectively as compared to the uncoated WC and monolayer TiN coated tool. Such improved performance of bilayer coating was found to be associated with its microstructure, mechanical and tribological properties. Existence of lubricious WS2 phase in the composite TiN–WSx layer along with superior coating adhesion and equivalent nanohardness as compared to TiN resulted in low cutting forces. Formation of W–O tribo layer on surface of worn-out coating on flank surface of tool aided in improving tool life during prolonged turning test.

Wear morphology of microwave post-treated WC-Co tool during machining of Inconel 718 superalloy

The study aims at reducing consumption of cutting fluid without affecting dry machining performance through application of microwave post-treated WC-Co insert. Microwave heating is an emerging route to volumetrically heat microwave absorbent materials (like tungsten carbide) at economical cost with less time as well energy. In the present study, performance of microwave treated (at 2.45 GHz frequency) carbide insert is studied while machining of Inconel 718 superalloys. Different modes of tool wear are investigated along with progression depth of flank wear. Experimental results are compared to that of untreated/ conventional insert. EDS analysis is carried out at different locations of worn-out WC-Co insert to analyze morphology of tool wear. Additionally, beneficial effects of microwave post-treatment of WC-Co insert are explained in terms of microhardness, wear resistance, and microstructural alteration. Finally, improved properties of microwave-treated WC-Co insert is correlated with machinability of Inconel 718.

The effect of a buffer layer on the structure and the performance of cutting-tools for ZrWN films that are deposited using DCMS and HIPIMS

This paper determines the optimal settings for the deposition of ZrWN nitride films using reactive direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS), with pure Zr and W metal targets and Ar plasma and N2 reactive gases. The materials tested as buffer layers are metal tungsten (W) and tungsten nitride (WN) thin films. Using a Taguchi method, this study determines the effect of deposition parameters for the buffer layer (W DC power, substrate bias, N2/(N2+Ar) flow rate and substrate temperature) on the structural and mechanical properties, and the dry machining performance of cutting-tools for multilayer ZrWN/W and ZrWN/WN/substrates. In the confirmation runs using grey Taguchi analysis, there is an improvement of 32.31% and 13.38% in surface roughness and flank wear, respectively. The films are characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (FEI-TEM) and a nanoindenter. The TEM pattern for the ZrWN films shown corresponds to the (111), (200) and (220) planes of the face-center-cubic phase. Pretreatment of a tungsten carbide tool uses oxygen plasma etching to enhance the adhesion of the multilayer ZrWN/WN coating. Compared with coatings that are deposited using DCMS, the samples that are deposited using HIPIMS exhibit a higher film density and a smoother surface. In the HIPIMS mode, the XRD diffraction peaks of the films are sharper and more intense, which indicates an improvement in crystallinity.

Improving dry machining performance of TiAlN hard-coated tools through combined technology of femtosecond laser-textures and WS2 soft-coatings

In this paper, we investigated the effects of WS2 solid lubricant film and femtosecond laser-textures on improving the cutting performance of PVD TiAlN coated tools, which is crucial for dry cutting applications. To do this, nano-scale textures were fabricated on the rake face of WC/Co-based TiAlN coated tools using femtosecond laser technology, WS2 solid lubricant film was then deposited on to the conventional and nano-scale textured TiAlN coated surfaces by medium-frequency magnetron sputtering technique. The microstructures and fundamental properties of the laser textured and WS2 coated surfaces were assessed utilizing the analytical tools. Dry cutting experiments were carried out on hardened steel with the developed TiAlN coated tools, and the resulting friction and wear data were compared with those from the conventional one. These tests show that, as WS2 film has much smaller shear strength than TiAlN coatings, the lubrication of contact between the tool/chip interface is enhanced. This leads to a significant improvement in the dry cutting performance of WS2 coated specimens, showing reductions in cutting forces, cutting temperatures, friction coefficient and tool wear compared with that of the conventional TiAlN coated tool. Another, important, finding is nano-scale textures on the TiAlN coating surfaces can improve the effective life of the initial WS2 layer for a longer period than the untextured one due to the higher adhesive strength between the WS2 and textured TiAlN films. The possible mechanisms for the effects of WS2 solid lubricant film and femtosecond laser-textures are discussed.

OPTIMIZATION OF CVD DIAMOND COATING TYPE ON MICRO DRILLS IN PCB MACHINING

The demand for better tools for machining printed circuit boards (PCBs) is increasing due to the extensive usage of these boards in digital electronic products. This paper is aimed at optimizing coating type on micro drills in order to extend their lifetime in PCB machining. First, the tribotests involving micro crystalline diamond (MCD), nano crystalline diamond (NCD) and bare tungsten carbide (WC-Co) against PCBs show that NCD–PCB tribopair exhibits the lowest friction coefficient (0.35) due to the unique nano structure and low surface roughness of NCD films. Thereafter, the dry machining performance of the MCD- and NCD-coated micro drills on PCBs is systematically studied, using diamond-like coating (DLC) and TiAlN-coated micro drills as comparison. The experiments show that the working lives of these micro drills can be ranked as: NCD[Formula: see text]TiAlN[Formula: see text]DLC[Formula: see text]MCD[Formula: see text]bare WC-Co. The superior cutting performance of NCD-coated micro drills in terms of the lowest flank wear growth rate, no tool degradation (e.g. chipping, tool tipping) appearance, the best hole quality as well as the lowest feed force may come from the excellent wear resistance, lower friction coefficient against PCB as well as the high adhesive strength on the underneath substrate of NCD films.

Performance of green machining: a comparative study of turning ductile cast iron FCD700

A safe and healthy workplace is important for sustainable manufacturing. Green machining is a metal cutting process that does not use a cutting fluid and, because it is less detrimental to the environment, it is fast being adopted by metal cutting industries. In conventional machining, Metal Working Fluids (MWFs) are widely used to obtain a smoother machining process, a longer tool life, and a better surface finish. Unfortunately, metalworking fluids also have several negative health, production cost, and environmental impacts. This paper focuses on an experimental investigation into the role of green or dry machining on tool life and surface finish, in the machining of ductile cast iron FCD700. A comparative study of turning experiments, under dry and wet cutting conditions, using commercial oil and palm oil-based MWFs, was conducted using the same machining parameter set-up. The results show that dry machining performance is comparable to that of wet machining. It was found that the performance of wet machining, in terms of tool life, was better than dry machining; however, the surface quality of dry machining was almost similar to that of wet machining. Furthermore, it was evident that green machining can be conducted at high cutting speeds, low feed rates, and depths of cut, and using suitable coated tools.

Adhesion analysis and dry machining performance of CVD diamond coatings deposited on surface modified WC–Co turning inserts

This paper investigates the effects of different surface pretreatments on the adhesion and performance of CVD diamond coated WC–Co turning inserts for the dry machining of high silicon aluminum alloys. Different interfacial characteristics between the diamond coatings and the modified WC–Co substrate were obtained by the use of two different chemical etchings and a CrN/Cr interlayer, with the aim to produce an adherent diamond coating by increasing the interlocking effect of the diamond film, and halting the catalytic effect of the cobalt present on the cemented carbide tool. A systematic study is analyzed in terms of the initial cutting tool surface modifications, the deposition and characterization of microcrystalline diamond coatings deposited by HFCVD synthesis, the estimation of the resulting diamond adhesion by Rockwell indentations and Raman spectroscopy, and finally, the evaluation of the dry machining performance of the diamond coated tools on A390 aluminum alloys. The experiments show that chemical etching methods exceed the effect of the CrN/Cr interlayer in increasing the diamond coating adhesion under dry cutting operations. This work provided new insights about optimizing the surface characteristics of cemented carbides to produce adherent diamond coatings in the dry cutting manufacturing chain of high silicon aluminum alloys.

Effect of Coating Thickness on the Characteristics and Dry Machining Performance of TiN Film Deposited on Cemented Carbide Inserts Using CFUBMS

This study deals with the effect of coating thickness on the characteristics and dry machining performance of TiN film deposited on cemented carbide inserts using closed-field unbalanced magnetron sputtering (CFUBMS). The turning inserts were coated with TiN film of varying thickness ranging from 1.8 µm to 6.7 µm. The deposited coatings were characterized using grazing incidence X-ray diffraction (GIXRD), Vickers and Knoop microhardness tester, and scratch tester. The machining performance of uncoated and coated carbide inserts was evaluated in dry turning of C40 steel. The in-house developed TiN-coated carbide insert exhibited around 16 times higher tool life compared to that of the uncoated insert. Performance test clearly showed the weakness of the uncoated K-type carbide relative to its TiN coated counterpart in machining of long chipping material like C40 steel. The present investigation clearly reveals that the developed TiN-coated tool has a potential for augmenting the cutting capability of uncoated K-type carbide, normally recommended for machining of short-chipping material like cast iron, for machining of even long-chipping material like steel.

Effect of cutting atmosphere on dry machining performance with Al2O3/ZrB2/ZrO2 ceramic tool

In this paper, Al2O3/ZrB2/ZrO2 ceramic cutting tool was produced by hot pressing. Dry cutting tests in air and nitrogen atmospheres were carried out on normalized AISI 1045 steel. The tool wear, cutting temperature, cutting force, and friction coefficient were measured. Compared in nitrogen, the friction coefficient in air was reduced when the cutting speed was higher than 160 m/min. Scanning electron microscopy and energy dispersive X-ray analysis techniques were employed to observe the worn surfaces of the ceramic tools, and the wear mechanisms were simultaneously discussed. Experimental data and observations revealed the formation of oxide film under air in dry machining, which related to the decrease of the friction coefficient and the improvement of cutting performance.

In-situ formation of self-lubricating tribo-films for dry machinability

Significant reductions in friction coefficient during sliding tests of Cl-implanted TiN films were attributed to tribological reactions leading to the formation of TiO and shear deformable Magneli phase oxide (Ti n O 2 n−1 ), which are thought to act as a self-lubricant. Turning tests using cutting tools with Cl-implanted TiN and TiCN protective coatings have resulted in reduced friction and wear. Two types of experiments have been carried out to study the formation of Ti-oxides in the presence of chlorine, and their relation to the improvement in dry machining performance. Firstly, unimplanted and Cl-implanted titanium films were oxidized in air at 400 °C to simulate in-situ oxidation in conditions similar to local heating during machining. Secondly, the oxide tribo-films formed on the cutting surface of unimplanted and implanted TiCN coated tools used in turning tests were examined in order to relate the oxide formation to improved cutting behaviour. Significantly greater amounts of TiO and intermediate Ti-oxides including TiO x (1 < x < 2) and Magneli phases were found in the Cl-implanted samples analysed by X-ray photoelectron spectroscopy (XPS) in comparison to the unimplanted samples. The implanted chlorine atoms may have a catalytic role in the formation of Ti-oxides from Ti or TiCN. Furthermore, chlorine forms bonds with titanium, which reduces vacancies for oxygen during the oxidation reactions. This results in the formation of the lower order Ti-oxides instead of TiO 2.

Effect of chromium content on the dry machining performance of magnetron sputtered Cr xC coatings

Physical vapor deposition (PVD)-coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in the high-speed machining operations. In this paper, the tribological characteristics and machining performance of chromium carbide (Cr x C)-coated cemented carbide tool inserts and micron-drills were assessed in dry machining. Cr x C coatings have been deposited with different optical emission monitoring (OEM) set values of chromium target “poisoning” by closed field unbalanced magnetron (CFUBM) sputtering and OEM control. The microstructures and mechanical properties of Cr x C coatings have been characterized by SEM, nanoindentation and adhesion techniques. The tribological properties of the coatings have been tested against different counterbodies under dry conditions using an oscillating friction and wear tester. Indexable inserts with Cr x C coatings were applied to turning AISI 1045 steel and JIS C5191 phosphor bronze material by a lathe. Micron-drills with Cr x C coatings were adopted in the ultra high speed (10 5 rpm) PCB through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the chromium content. Cr 0.182C-coated inserts showed the best wear resistance in 1045 steel turning test. Cr 0.688C-coated tools have excellent performance in both phosphor bronze turning and PCB through-hole drilling tests. The service life of Cr 0.688C-coated tool is 15 times greater than that of an uncoated tool in PCB through-hole drilling test.

Influence of chromium content on the dry machining performance of cathodic arc evaporated TiAlN coatings

Physical vapour deposition (PVD) titanium aluminium nitride coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in a number of aggressive metal-cutting operations, namely, dry and high-speed machining. In this investigation, the performance of Ti 1− x Al x N and Ti 1− x− y Al x Cr y N coatings was assessed on Co-HSS twist drills used to machine grey cast iron. The failure criterion for drills was defined as a critical sized flank wear land at the outer corners of the drills. Using this criterion, the average tool life of uncoated twist drills was increased by factors of 2.5, 3.0 and 3.0 by Ti 0.59Al 0.41N, Ti 0.27Al 0.19Cr 0.54N and Ti 0.21Al 0.14Cr 0.65N coatings, respectively. Notwithstanding the similar increase in average tool life, the Ti 1− x− y Al x Cr y N coatings produced more consistent results than the Ti 1− x Al x N coated drills with standard deviations of 67, 3 and 19 holes, respectively. This result has significant practical implications in manufacturing, since drills are not replaced on an individual basis, but rather on a preset tool change frequency. The present paper discusses the performance of Ti 1− x Al x N and Ti 1− x− y Al x Cr y N coated drills in terms of average and practical drill life and concludes with remarks on the characterisation of PVD coatings and their significance on the performance of Co-HSS twist drills when dry machining grey cast iron.