Tribological investigation of TiAlCrN and TiAlN/CrN coatings grown by combined steered-arc/unbalanced magnetron deposition

Luo, Quanshun; Rainforth, W. M.; Donohue, L.A.; Wadsworth, I.; Münz, W.‐D.

doi:10.1016/s0042-207x(98)00406-0

Cited by 46 publications

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“…The result from calculation of a single, isolated, impurity within the AlN host is seen in figure 4.5, where the electron DOS has been calculated in both cubic B1 and hexagonal B4 structures, as well as with both PBE and mHSE functionals. In the B1 structure, for both functionals, the impurity states within the band gap maintain a purely t 2g nature, pointing along the [110] fcc directions, towards the Al sites and away from the large charge concentration on the N-sites in the [100] directions. The e g orbitals on the other hand are well separated from the t 2g orbitals and situated inside the conduction band, regardless of functional used.…”

Section: Resultsmentioning

confidence: 99%

“…The B1 supercell is a 4x2x4 fcc lattice and the B4 supercell is a 2x4x2 hexagonal lattice, both structures have a total of 64 atoms. In the B1 structures the structures are two atoms whose relative positions were determined through the techniques of SQS and fairly well separated (1), two impurities as nearest neighbors along the [110] direction of the metal fcc sublattice (2) and two atoms as second nearest neighbors along the [100] direction (3). Consequently structure (1) is intended to represent, as far as possible, an infinitely large random arranged alloy, structure (2) has two close lying impurities with overlapping t 2g orbitals and structure (3) have the impurities close by, but screened by a N-atom between them and the t 2g orbitals are all pointing towards Al-sites.…”

Section: Local Environment and Magnetic Phasesmentioning

confidence: 99%

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Theoretical understanding of stability of alloys for hard-coating applications and design

Lind¹

2015

Linköping Studies in Science and Technology. Dissertations

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The performance of modern hard coating materials puts high demands on properties such as hardness, thermal stability and oxidation resistance. These properties not only depend on the chemical composition, but also on the structure of the material on a nanoscale. This kind of nanostructuring will change during use and can be both beneficial and detrimental as materials grown under non-equilibrium conditions transforms under heat treatment or pressure into other structures with significantly different properties. This thesis aims to reveal the physics behind the processes of phase stability and transformations and how this can be utilized to improve on the properties of this class of alloys. This has been achieved through the application of various methods of first-principles calculations and analysis of the results on the basis of thermodynamics and electronic structure theory.Within multicomponent transition metal aluminum nitride alloys (TMAlN) a number of studies have been carried out and presented here on ways of improving high temperature stability and hardness. Most (TMAl)N and TMN prefer a cubic B1 structure while AlN is stable in a hexagonal B4 phase, but for the purposes of hard coatings the metastable cubic B1 AlN phase, isostructural with the TMN phase is desired. It will be shown how the introduction of additional alloying components, such as Cr, into (TiAl)N changes the thermodynamic stability of phases so that new intermediary and metastable phases are formed during decomposition. In the case of such a (CrAl)N phase it is shown to have greater thermodynamic stability in the cubic phase than the pure AlN, resulting in improved high temperature hardness. Also, the importance of treating not just the binodal decomposition through the formation energy relative to end products but also the impact of spinodal decomposition from its second derivative due to the topology of formation energy surfaces is emphasized in the thesis. The impact of pressure on the AlN phase has also been studied through the calculation of a P-T diagram of AlN as part of a (TiAl)N alloy.During the study of chemical alloying of TM components into AlN the alloying of low concentrations of these TM were treated in great detail. What is generally referred to as the AlN phase in decomposition is not entirely pure and can be expected to contain traces of any alloying components, such as Ti and Cr or whatever other metals may be present. Low concentration alloying of Cr, on the order of 5-10% is also shown to be stable with regard to isostructural decomposition. Detailed analysis of the effect of Ti and Cr impurities in AlN has been carried out along with a systematic search of AlN alloyed with small amounts of other TM components. The impact of these impurities on the electronic structure and thermodynamic properties is analyzed and the general trends will be explained through the occupation of impurity states by d-like electrons.iv Theoretical treatment of such impurities is not straightforward however. AlN is an s-p semiconduct...

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Section: Resultsmentioning

confidence: 99%

Section: Local Environment and Magnetic Phasesmentioning

confidence: 99%

Theoretical understanding of stability of alloys for hard-coating applications and design

Lind¹

2015

Linköping Studies in Science and Technology. Dissertations

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“…Various studies have shown that the performance of these coatings may outperform Ti-Al-N coatings [24][25][26][27]67 . The fundamental mechanisms that yield these enhanced properties were not understood at the beginning of this work.…”

Section: Ti-cr-al-nmentioning

confidence: 99%

Multicomponent Alloying for Improved Hard Coatings

Forsén¹

2014

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The cover image shows an energy dispersive elemental map of a Ti-Cr-Al-N coating heated at 1100 ºC for 2 hours, Ti (red), Cr (blue) and Al (green). The domain size is around 20 nanometers.© Rikard Forsén, unless otherwise stated ISSN: 0345-7524 Printed by LiU-Tryck, Linköping, Sweden, 2014 AbstractCoatings are vital to protect and to increase the productivity of cutting tools in high speed and dry cutting applications. During the cutting operation the temperature may exceed 1000 ºC it is therefore necessary that the coatings withstand high temperatures. A lot of development and research has been carried out during the last 30 years on finding new coating material systems providing enhanced properties such as adhesion, hardness and oxidation resistance at elevated temperatures. This thesis is based on multicomponent alloying of quaternary transition metal nitride hard coatings with a main focus on Ti-CrAl-N coatings. Many different coatings and compositions have been deposited using an industrial scale cathodic arc evaporation deposition system. All deposited coatings contain Al as this element is known to increase the hardness and the oxidation resistance of nitride coatings. The deterioration of the hardness in Al-containing nitride coatings is generally attributed to the transformation of cubic Al-N into hexagonal Al-N and the consequent domain coherency relaxation. This thesis investigates these phenomena on an atomic level providing a deeper understanding of and a way to engineer improved hard nitride coatings. The essence of this thesis is that by adding a third metal to a ternary nitride material system, for example one of the most frequently used Ti-Al-N, it is possible to tune and engineer the thermal stability of the cubic structure and the coherency strain which in turn affects the hardness and the oxidation resistance. The key point is that new intermediate phases in the decomposition process are generated so that the eventual detrimental phases are suppressed and delayed. More specifically, when Cr is added to the Ti-Al-N material system the coatings exhibit an age hardening process up to 1000 ºC caused by spinodal decomposition into coherent TiCr-and AlCr-rich cubic TiCr-Al-N domains. This means that the unstable cubic Ti-Cr-Al-N phase decomposes via yet another unstable cubic Cr-Al-N phase before the detrimental hexagonal transformation of Al-N takes place. The hardness is therefore retained up to a higher temperature compared to Ti-Al-N coatings.By utilizing multicomponent alloying through addition of Ti to Cr-Al-N coatings the hardness is retained after annealing up to 1100 ºC. This is a dramatic improvement compared to Cr-Al-N coatings. Here the Ti addition promotes the competitive spinodal decomposition into TiCr-and Al-enriched domains suppressing the detrimental hexagonal Al-N formation.To investigate the effect of multicomponent alloying for other material systems with different mixing free energies and atomic sizes, Zr-containing, Zr-Cr-Al-N and Zr-Ti-Al-N, quaternary nitride coatings ...

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“…[7][8][9] Another approach is alloying TiAlN with Cr which has shown promising results by introducing intermediate decomposition steps yielding improved hardness, oxidation, and wear resistance. [10][11][12][13][14][15][16][17] Cr-alloyed TiAlN coatings exhibit spinodal decomposition at 900-1000 C into coherent nanometer-sized c-TiCr(Al)N and c-(TiCr)AlN domains during which the hardness increases (where elements within parentheses indicate a low content). The lattice parameter of c-CrN is in-between c-TiN and c-AlN (Ref.…”

Section: Introductionmentioning

confidence: 99%

Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability

Forsén

Ghafoor

Odén

2013

Journal of Applied Physics

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A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti 1Àx Cr x N multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti-and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti 1Àx Cr x N layers. For x ¼ 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > ¼0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials. V C 2013 AIP Publishing LLC. [http://dx

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Tribological investigation of TiAlCrN and TiAlN/CrN coatings grown by combined steered-arc/unbalanced magnetron deposition

Cited by 46 publications

References 0 publications

Theoretical understanding of stability of alloys for hard-coating applications and design

Theoretical understanding of stability of alloys for hard-coating applications and design

Multicomponent Alloying for Improved Hard Coatings

Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability

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