Special Issue "Coatings for Cutting Tools"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (31 January 2018).

Special Issue Editor

Guest Editor
Prof. Dr. James E. Krzanowski Website E-Mail
Mechanical Engineering Department, University of New Hampshire, Kingsbury Hall, 33 Academic Way, Durham, NH 03824, USA
Phone: +1-603-862-1865
Fax: +1 603 862 1865
Interests: nitrides; carbides; sputter deposition; ion-assisted deposition; wear; friction; tool coatings

Special Issue Information

Dear Colleagues,

The application of hard and lubricious coatings to cutting tools has provided substantial benefits to the metal cutting industry by reducing wear and greatly increasing the useful life of tools. Coatings have gone through several generations of development, due to the increasing demands of the industry, such as high-speed machining, dry machining, and machining of difficult-to-cut alloys, such as superalloys and titanium. The first coatings developed were hard coatings of TiN, TiC, TiCN or aluminum oxide, and were often used in a multiple layers; materials with these coatings outperformed uncoated high-speed steel inserts, due to their superior hardness and wear resistance. However, TiN is limited in application due to oxidation at high temperatures, and TiC has a relatively low hot hardness. The next generation of coatings focused on TiAlN, with varying Ti/Al ratios. These films exhibited increased hardness and wear resistance, as well as improved chemical stability and lower thermal conductivity than the previous generation of coatings exhibited.

Despite these advances, further improvements are needed to develop coatings that will meet the needs of increasingly severe cutting environments.  One approach currently under investigation is to alloy TiAlN with elements such as Cr, Y or V, which can provide coatings with higher hardness and improved oxidation resistance.  In addition, in some cases, the oxides of certain elements, such as Cr or V, can be lubricious and therefore reduce tool cutting forces.  Nanostructured multilayer films, such as TiAlN/CrN and TiAlN/VN represent another approach to reducing tool wear and have received considerable attention from the research community.

This Special Issue of Coatings is intended to provide a forum for original research articles as well as critical reviews on current advances in the field of coatings for machining applications. Areas of interest include, but are not limited to, advanced nitride, carbide, and oxide coatings, nanoscale multilayer coatings, nano-composite coatings, and coatings that provide reduced friction during machining applications.  Aspects of research of interest include structural investigations of advanced coatings, deposition methods for coating cutting tools, laboratory testing methods, as well as machining studies and in-situ coating evaluations.

Prof. Dr. James E. Krzanowski
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Published Papers (9 papers)

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Research

Open AccessArticle
Investigation into Performance of Multilayer Composite Nano-Structured Cr-CrN-(Cr0.35Ti0.40Al0.25)N Coating for Metal Cutting Tools
Coatings 2018, 8(12), 447; https://doi.org/10.3390/coatings8120447 - 06 Dec 2018
Abstract
This paper deals with the Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating. It has a three-layered architecture with a nano-structured wear-resistant layer. The studies involved the investigation into the microstructure (with the use of SEM and TEM), elemental and phase composition (XRD [...] Read more.
This paper deals with the Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating. It has a three-layered architecture with a nano-structured wear-resistant layer. The studies involved the investigation into the microstructure (with the use of SEM and TEM), elemental and phase composition (XRD and SAED patterns), wear process pattern in scratch testing, crystal structure, as well as the microhardness of the coating. Cutting tests of tools with the above coating were carried out in dry turning of steel 1045 at cutting speeds of vc = 200, 250, and 300 m·min−1. The comparison included uncoated tools and tools with the commercial TiN and (Ti,Al)N coatings with the same thickness. The tool with the Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating showed the longest tool life at all the cutting speeds under consideration. Meanwhile, a tool with the coating under study can be recommended for use in turning constructional steel at the cutting speed of vc = 250 m·min−1. At this cutting speed, a tool shows the combination of a rather long tool life and balanced wear process, without any threat of catastrophic wear. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Effect of Hexagonal Phase Content on Wear Behaviour of AlTiN Arc PVD Coatings
Coatings 2018, 8(2), 72; https://doi.org/10.3390/coatings8020072 - 13 Feb 2018
Cited by 2
Abstract
In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content [...] Read more.
In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content in the AlTi source material was increased from 67 to 73 at.%. We applied two settings of the magnetic field that steers the arc across the cathode surface thereby evaporating the AlTi alloy differently. The resulting coating thickness ranged from 3.5 to about 7 µm. Cemented tungsten carbide was used as substrate material. Coating properties like hardness, adhesion, and crystal phases were analyzed by indentation and X-ray diffraction, respectively. The wear behaviour of the different AlTiN hard coatings were investigated in two ways. In a first idealized test, cyclic impacting was done applying a constant force. The resulting wear pattern was quantified by an Alicona multi-focus microscope. A second wear test was done by metal cutting under realistic conditions. Fly milling of ductile cast iron (EN-GJS-700) was performed with regular interruptions in order to measure the increasing wear mark. As expected, aluminium contents above 67 at.% (in the metal fraction of the coating) lead to a decreased wear resistance as the soft hexagonal phase exceeds values of a few vol.%. However, it was found that the formation of the hexagonal phase can be effectively influenced and delayed by increasing the magnetic steering field at the cathode. The wear behavior observed in cyclic impact testing corresponds well to results obtained with the more complex loading situation encountered in milling. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Improvement of Wear Performance of Nano-Multilayer PVD Coatings under Dry Hard End Milling Conditions Based on Their Architectural Development
Coatings 2018, 8(2), 59; https://doi.org/10.3390/coatings8020059 - 05 Feb 2018
Cited by 2
Abstract
The TiAlCrSiYN-based family of PVD (physical vapor deposition) hard coatings was specially designed for extreme conditions involving the dry ultra-performance machining of hardened tool steels. However, there is a strong potential for further advances in the wear performance of the coatings through improvements [...] Read more.
The TiAlCrSiYN-based family of PVD (physical vapor deposition) hard coatings was specially designed for extreme conditions involving the dry ultra-performance machining of hardened tool steels. However, there is a strong potential for further advances in the wear performance of the coatings through improvements in their architecture. A few different coating architectures (monolayer, multilayer, bi-multilayer, bi-multilayer with increased number of alternating nano-layers) were studied in relation to cutting-tool life. Comprehensive characterization of the structure and properties of the coatings has been performed using XRD, SEM, TEM, micro-mechanical studies and tool-life evaluation. The wear performance was then related to the ability of the coating layer to exhibit minimal surface damage under operation, which is directly associated with the various micro-mechanical characteristics (such as hardness, elastic modulus and related characteristics; nano-impact; scratch test-based characteristics). The results presented exhibited that a substantial increase in tool life as well as improvement of the mechanical properties could be achieved through the architectural development of the coatings. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Cutting Performance of Low Stress Thick TiAlN PVD Coatings during Machining of Compacted Graphite Cast Iron (CGI)
Coatings 2018, 8(1), 38; https://doi.org/10.3390/coatings8010038 - 18 Jan 2018
Cited by 5
Abstract
A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of [...] Read more.
A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of PVD coatings as thick as 15 µm. In some applications, in particular for machining of such hard to cut material as compacted graphite iron (CGI), such coatings have shown better tool life compared to the conventional PVD coatings that have a lower thickness in the range of up to 5 μm. Finite element modeling of the temperature/stress profiles was done for the SFC coatings to present the temperature/stress profiles during cutting. Comprehensive characterization of the coatings was performed using XRD, TEM, SEM/EDS studies, nano-hardness, nano-impact measurements, and residual stress measurements. Application of the coating with this set of characteristics reduces the intensity of buildup edge formation during turning of CGI, leading to longer tool life. Optimization of the TiAlN-based coatings composition (Ti/Al ratio), architecture (mono vs. multilayer), and thickness were performed. Application of the optimized coating resulted in a 40–60% improvement in the cutting tool life under finishing turning of CGI. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Titanium Aluminium Nitride and Titanium Boride Multilayer Coatings Designed to Combat Tool Wear
Coatings 2018, 8(1), 12; https://doi.org/10.3390/coatings8010012 - 28 Dec 2017
Cited by 4
Abstract
The lifetimes and the premature wear of machining tools impact on manufacturing efficiencies and productivities. A significant proportion of machining tool damage can be attributed to component wear. Here, titanium aluminium nitride (TiAlN) multi-layered with titanium diboride (TiB2) prepared by PVD [...] Read more.
The lifetimes and the premature wear of machining tools impact on manufacturing efficiencies and productivities. A significant proportion of machining tool damage can be attributed to component wear. Here, titanium aluminium nitride (TiAlN) multi-layered with titanium diboride (TiB2) prepared by PVD (Physical Vapour Deposition) sputtering onto H-13 substrates are studied as potential wear-resistant coatings for forging die applications. The TiB2 content has been altered and two-sets of coating systems with a bilayer thickness either less than or greater than 1 μm are investigated by tribological and microstructural analysis. XRD analysis of the multilayers reveals the coatings to be predominately dominated by the TiAlN (200) peak, with additional peaks of TiN (200) and Ti (101) at a TiB2 content of 9%. Progressive loads increasing to 100 N enabled the friction coefficients and the coating failure at a critical load to be determined. Friction coefficients of around 0.2 have been measured in a coating containing 9% TiB2 at critical loads of approximately 70 N. Bi-directional wear tests reveal that bilayers with thicknesses greater than 1 μm have frictional coefficients that are approximately 50% lower than those where the bilayer is less than 1 μm. This is due to the greater ability of thicker bilayers to uniformly distribute the stress within the layers. There are two observed frictional coefficient regimes corresponding to a lower and higher rate of material loss. At the lower regime, with TiB2 contents below 20%, material loss occurs mainly via delamination between the layers, whilst at compositions above this, material loss occurs via a break-up of material into finer particles that in combination with the higher loads results in greater material loss. The measured wear scar volumes for the TiAlN/TiB2 multilayer coatings are approximately three times lower than those measured on the substrate, thus validating the increased wear resistance offered by these composite coatings. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Tribological and Wear Performance of Carbide Tools with TiB2 PVD Coating under Varying Machining Conditions of TiAl6V4 Aerospace Alloy
Coatings 2017, 7(11), 187; https://doi.org/10.3390/coatings7110187 - 04 Nov 2017
Cited by 5
Abstract
Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the [...] Read more.
Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the cutting tool is strongly associated with the conditions of the machining process. The present work shows the effect of different machining conditions on the tribological and wear performance of TiB2-coated cutting tools compared to uncoated carbide tools. FEM modeling of the temperature profile on the friction surface was performed for wet machining conditions under varying cutting parameters. Comprehensive characterization of the TiB2 coated vs. uncoated cutting tool wear performance was made using optical 3D imaging, SEM/EDX and XPS methods respectively. The results obtained were linked to the FEM modeling. The studies carried out show that during machining of the TiAl6V4 alloy, the efficiency of the TiB2 coating application for carbide cutting tools strongly depends on cutting conditions. The TiB2 coating is very efficient under roughing at low speeds (with strong buildup edge formation). In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Hybrid Ti-MoS2 Coatings for Dry Machining of Aluminium Alloys
Coatings 2017, 7(9), 149; https://doi.org/10.3390/coatings7090149 - 16 Sep 2017
Cited by 4
Abstract
Combinatorial deposition, comprising filtered cathodic vacuum arc (FCVA) and physical vapor deposition (PVD) magnetron sputtering is employed to deposit molybdenum disulphide (MoS2) and titanium (Ti) thin films onto TiB2-coated tool inserts specifically designed for the dry machining of aluminium [...] Read more.
Combinatorial deposition, comprising filtered cathodic vacuum arc (FCVA) and physical vapor deposition (PVD) magnetron sputtering is employed to deposit molybdenum disulphide (MoS2) and titanium (Ti) thin films onto TiB2-coated tool inserts specifically designed for the dry machining of aluminium alloys. Titanium is deposited by FCVA while MoS2 is magnetron sputtered. The deposition set up allows several compositions of Ti-MoS2 to be deposited simultaneously, with Ti content ranging between 5 and 96 at. %, and their machining performances to be evaluated. Milling took place using a CNC Vertical Machining Center at a 877 mm/min feed rate. The effect of different coating compositional ratios on the degree of aluminium sticking when a milling insert is used to face mill an Al alloy (SAE 6061) was investigated using a combination of energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. XPS studies suggest that the greater degree of Al sticking on the rake face of the inserts is due to the formation of greater amounts of non-protective Ti-O phases. EDX mapping of the milling inserts after machining reveal that a Ti:MoS2 ratio of around 0.39 prevents Al from sticking to the tool edges. Since we prevent Al from sticking to the tool surface, the resultant machined surface finish is improved thus validating the machining performance of TiB2-coated tools using optimum compositions of Ti:MoS2 thin film coatings. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Investigation of Coated Cutting Tool Performance during Machining of Super Duplex Stainless Steels through 3D Wear Evaluations
Coatings 2017, 7(8), 127; https://doi.org/10.3390/coatings7080127 - 17 Aug 2017
Cited by 11
Abstract
In this study, the wear mechanisms and tribological performance of uncoated and coated carbide tools were investigated during the turning of super duplex stainless steel (SDSS)—Grade UNS S32750, known commercially as SAF 2507. The tool wear was evaluated throughout the cutting tests and [...] Read more.
In this study, the wear mechanisms and tribological performance of uncoated and coated carbide tools were investigated during the turning of super duplex stainless steel (SDSS)—Grade UNS S32750, known commercially as SAF 2507. The tool wear was evaluated throughout the cutting tests and the wear mechanisms were investigated using an Alicona Infinite Focus microscope and a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Tribo-film formation on the worn rake surface of the tool was analyzed using X-ray Photoelectron Spectroscopy (XPS). In addition, tribological performance was evaluated by studying chip characteristics such as thickness, compression ratio, shear angle, and undersurface morphology. Finally, surface integrity of the machined surface was investigated using the Alicona microscope to measure surface roughness and SEM to reveal the surface distortions created during the cutting process, combined with cutting force analyses. The results obtained showed that the predominant wear mechanisms are adhesion and chipping for all tools investigated and that the AlTiN coating system exhibited better performance in all aspects when compared with CVD TiCN + Al2O3 coated cutting insert and uncoated carbide insert; in particular, built-up edge formation was significantly reduced. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle
Machining Duplex Stainless Steel: Comparative Study Regarding End Mill Coated Tools
Coatings 2016, 6(4), 51; https://doi.org/10.3390/coatings6040051 - 26 Oct 2016
Cited by 14
Abstract
The difficulties in the machining of duplex stainless steel are well known. However, research on this matter is rather limited. Suppliers offer quite different cutting tools for the same raw material, with end mills of two, three or even four knives and a [...] Read more.
The difficulties in the machining of duplex stainless steel are well known. However, research on this matter is rather limited. Suppliers offer quite different cutting tools for the same raw material, with end mills of two, three or even four knives and a huge number of distinct coatings, some of them under commercial brands, making it difficult to assess the advantages they offer. Furthermore, there is a remarkable difference among the several types of duplex stainless steel available nowadays on the market. The present work intends to assess the machining performance of different tools, analyzing the behavior and wear mechanisms with two different cutting lengths, keeping constant the machining trajectory. Some other parameters were also kept constant, such as cutting speed, depth of cut and cutting width, as well as feed per tooth. The machining process was carried out under lubricated conditions, using an emulsion of 5% oil in water. Tools provided with a different number of teeth and surface coatings were tested, analyzing the wear behavior of each cutting length using scanning electron microscopy, trying to identify wear performance and how each coating contributes to increased tool life. The surfaces produced were also analyzed by means of profilometry measurements, correlating tool wear and part surface roughness. This comparative study allows determining the advantages of different tools relative to others, based on coatings and tool geometry. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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