| 1. |
- Eriksson, Anders, et al.
(author)
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Layer Formation by Resputtering in Ti-Si-C Hard Coatings during Large Scale Cathodic Arc Deposition
- 2011
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 205:15, s. 3923-3930
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Journal article (peer-reviewed)abstract
- This paper presents the physical mechanism behind the phenomenon of self-layering in thin films made by industrial scale cathodic arc deposition systems using compound cathodes and rotating substrate fixture. For Ti-Si-C films, electron microscopy and energy dispersive x-ray spectrometry reveals a trapezoid modulation in Si content in the substrate normal direction, with a period of 4 to 23 nm dependent on cathode configuration. This is caused by preferential resputtering of Si by the energetic deposition flux incident at high incidence angles when the substrates are facing away from the cathodes. The Ti-rich sub-layers exhibit TiC grains with size up to 5 nm, while layers with high Si-content are less crystalline. The nanoindentation hardness of the films increases with decreasing layer thickness.
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| 2. |
- Eriksson, Anders, et al.
(author)
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Ti-Si-C-N Thin Films Grown by Reactive Arc Evaporation from Ti3SiC2 Cathodes
- 2011
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In: Journal of Materials Research. - : Cambrdige University Press. - 0884-2914 .- 2044-5326. ; 26, s. 874-881
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Journal article (peer-reviewed)abstract
- Ti-Si-C-N thin films were deposited onto WC-Co substrates by industrial scale arc evaporation from Ti3SiC2 compound cathodes in N2 gas. Microstructure and hardness were found to be highly dependent on the wide range of film compositions attained, comprising up to 12 at.% Si and 16 at.% C. Nonreactive deposition yielded films consisting of understoichiometric TiCx, Ti and silicide phases with high (27 GPa) hardness. At a nitrogen pressure of 0.25-0.5 Pa, below that required for N saturation, superhard, 45-50 GPa, (Ti,Si)(C,N) films with a nanocrystalline feathered structure were formed. Films grown above 2 Pa displayed crystalline phases of more pronounced nitride character, but with C and Si segregated to grain boundaries to form weak grain boundary phases. In abundance of N, the combined presence of Si and C disturb cubic phase growth severely and compromises the mechanical strength of the films.
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| 3. |
- Flink, Axel, et al.
(author)
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Influence of Si on the Microstructure of Arc Evaporated (Ti,Si)N Thin Films : Evidence for Cubic Solid Solutions and their Thermal Stability
- 2005
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In: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 200:5-6, s. 1535-1542
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Journal article (peer-reviewed)abstract
- Ti1−xSixN (0 ≤ x ≤ 0.14) thin solid films were deposited onto cemented carbide (WC-Co) substrates by arc evaporation. X-ray diffraction and transmission electron microscopy showed that all films were of NaCl-structure type phase. The as-deposited films exhibited a competitive columnar growth mode where the structure transits to a feather-like nanostructure with increasing Si content. Films with 0 ≤ x ≤ 0.01 had a 111 crystallographic preferred orientation which changed to an exclusive 200 texture for 0.05 ≤ x ≤ 0.14. X-ray photoelectron spectroscopy revealed the presence of Si–N bonding, but no amorphous Si3N4. Band structure calculations performed using a full potential linear muffin tin orbital method showed that for a given NaCl-structure Ti1−xSixN solid solution, a phase separation into cubic SiN and TiN is energetically favorable. The microstructure was maintained for the Ti0.86Si0.14N film annealed at 900 °C, while recrystallization in the cubic state took place at 1100 °C annealing during 2 h. The Si content influenced the film hardness close to linearly, by combination of solid-solution hardening in the cubic state and defect hardening. For x = 0 and x = 0.14, nanoindentation gave a hardness of 31.3 ± 1.3 GPa and 44.7 ± 1.9 GPa, respectively. The hardness was retained after annealing at 900 °C, while it decreased to below 30 GPa for 1100 °C following recrystallization and W and Co interdiffusion.
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| 4. |
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| 5. |
- Hörling, Anders, et al.
(author)
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Phase stability and structural properties of Ti1-zZrzN (0<z<1) thin films
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Other publication (other academic/artistic)abstract
- Single-phase [NaCl]-structure Ti1-zZrzN thin films (0<z<1) have been deposited using cathodic arc plasma deposition. The films were investigated using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and nanoindentation. Theoretical calculations on phase stabilities using density-functional theory revealed that the pseudo-binary TiN-ZrN system exhibits a miscibility gap, with respect to phase transformation from the as-deposited single-phase [NaCl] structure into [NaCl]-strueture TiN and ZrN components up to 980°C for z=0.35. The films were found to retain their as-deposited single-phase [NaCl] structure during post-deposition annealing for 120 min at 600, 700, 1100 and 1200°C, and for as long as 195 h at 600°C. This effective thermal stability is explained by a limited driving force for phase transformation and insufficient atom diffusivity. For two film compositions deepest within the miscibility gap, however, results from nanoindentation show an essentially retained hardness at ~30 GPa after annealing at 1100-1200°C. The principal hardening mechanism for the Ti1-zZrzN fihns is thus proposed to be solid-solution hardening through localized lattice strain fields originating from difference in atomic radius of Ti and Zr. This particular system offers interesting opportunities for fundamental studies of time-temperature-transformations of ternary nitride thin films.
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| 6. |
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| 7. |
- Hörling, Anders, et al.
(author)
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Thermal stability, microstructure and mechanical properties of Ti1 − xZrxN thin films
- 2008
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 516:18, s. 6421-6431
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Journal article (peer-reviewed)abstract
- Single-phase [NaCl]-structure Ti1 − xZrxN thin films (0 < x < 1) have been deposited using cathodic arc plasma deposition. The films were investigated using X-ray diffraction (XRD), transmission electron microscopy, differential scanning calorimetry (DSC), and nanoindentation. Density functional theory calculations on phase stabilities show that the pseudo-binary TiN–ZrN system exhibits a miscibility gap, extending over 0 ≤ x ≤ 0.99 at 1000 °C, with respect to phase transformation from a solid solution into a two-phase mixture of [NaCl]-structure TiN and ZrN components. The films were found to retain their as-deposited single-phase structure during post-deposition annealing at 600 °C (18 h), 700 °C (12 h), 1100 and 1200 °C (2 h), and for as long as 195 h at 600 °C. DSC revealed no heat flow during annealing, similar to TiN, and only the x = 0.53 film exhibited a slight increase in XRD peak broadening after annealing at 1200 °C, consistent with spinodal decomposition. This effective thermal stability of the alloys is explained by the combination of a limited driving force for phase transformation and an insufficient atom diffusivity. In terms of mechanical properties, films with composition deepest within the miscibility gap showed a hardness of ∼ 30 GPa after annealing at 1100–1200 °C; a value only moderately lower than in the as-deposited condition. The principal hardening mechanism for the Ti1 − xZrxN films is proposed to be solid-solution hardening through local lattice strain fields originating from difference in atomic radius of Ti and Zr. The material system is thus promising for cutting tool applications.
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| 8. |
- Hörling, Anders, et al.
(author)
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Thermal stability of arc evaporated high aluminum-content Ti1−xAlxN thin films
- 2002
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 20:5, s. 1815-1823
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Journal article (peer-reviewed)abstract
- The thermal stability of Ti1−xAlxN films deposited by arc evaporation from Ti–Al cathodes with 67 and 75 at. % aluminum, respectively, has been investigated. The microstructure of as-deposited and isothermally annealed samples were studied using scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The chemical composition and elemental distribution were determined by energy dispersive x ray (EDX), Rutherford backscattering spectrometry, and EDX mapping. Transmission electron micrographs revealed a dense and columnar microstructure in the as-deposited condition. Films deposited from the 67 at. % cathodes were of cubic NaCl-structure phase, whereas films deposited from the 75 at. % cathodes exhibited nanocrystallites of wurzite-structure hexagonal-phase AlN in a cubic (c)-(Ti,Al)N matrix. Both films were stable during annealing at 900 °C/120 min with respect to phase composition and grain size. Annealing at 1100 °C of films deposited from the 67 at. % cathodes resulted in phase separation of c-TiN and h-AlN, via spinodal decomposition of c-TiN and c-AlN. (Ti,Al)N films undergo extensive stress relaxation and defect annihilation at relatively high temperatures, and aspects of these microstructural transformations are discussed.
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| 9. |
- Mayrhofer, Paul H., et al.
(author)
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Self-organized nanostructures in the Ti-Al-N system
- 2003
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 83:10, s. 2049-2051
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Journal article (peer-reviewed)abstract
- The phenomenon of age hardening could be evidenced in thin film applications. A model system, Ti1-xAlxN was chosen as such coatings are known for their excellent wear resistance enabling improved machining processes like high-speed and dry cutting. Here, we show unambiguously that metastable Ti1-xAlxN coatings initially undergo spinodal decomposition into coherent cubic-phase nanometer-size domains, causing an increase in hardness at elevated temperatures. These intermediate metastable domains transform into their stable phases TiN and AlN during further thermal treatment. Activation energies for the processes indicate defect-assisted segregation of Ti and Al. The findings are corroborated by ab initio calculations. A long-standing discussion on the thermal stability of this important class of ceramics is thus resolved.
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| 10. |
- Sjölén, Jacob, 1977-
(author)
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Arc evaporated wear-resistant nitride coatings for metal cutting tools
- 2008
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Licentiate thesis (other academic/artistic)abstract
- This Thesis is dedicated to increase the understanding of arc evaporated PVD coatings as wear resistant layers on metal cutting tools. The approach is to study coatings that have excellent performance in metal cutting applications, specifically (Ti,Al)N and (Ti,Si)N in terms of thermal and mechanical properties, and to correlate this to their microstructure, stress state, and composition. The effect of addition of oxygen into (Ti,Al)N is also evaluated in terms of structure, chemical bonding, and mechanical properties. It is shown that metastable fcc-(Ti,Al)N coatings separate into Ti-rich and Al-rich fcc-(Ti,Al)N zones via spinodal decomposition at 800 - 1000 °C, which acts as a hardening mechanism. This is followed by nucleation and growth into the stable phases fcc-TiN and hex-AlN at T>1000°C, with subsequent loss of hardness. These structural changes are correlated to the cutting performance, showing that the initial spinodal phase separation improves the performance. The success of (Ti,Al)N in metal cutting applications is, hence, due not only to the well documented oxidation resistance, but also to the spinodal decomposition process, which is active at the typical temperatures at the cutting edge of an engaged cutting insert. The potential subsequent renucleation process is, however, detrimental in metal cutting applications. Oxygen is commonly regarded as a contamination in PVD coating processes due to the risk of formation of insulating layers. This study, however, shows that by using arcevaporation, up to 35 at.% O can be incorporated into (Ti,Al)N coatings without altering its NaCl-structure. 1t is inferred that O substitutes for N in the lattice and (Ti,Al)(O,N) is formed. The incorporation of small amounts of oxygen (up to 13 at.%) improves the cutting performance by reducing the risk of chipping. However, at higher oxygen levels, the wear resistant properties are dramatically reduced. Finally, is shown that it is poss ible to replace at least 14 at.% Ti by Si, without altering the NaCl-structure in (Ti,Si)N coatings. The measured hardness of solid solution fcc-(Ti,Si)N is nearly a linear function of Si-content in the coating (from 31 GPa in TiN up to 45 GPa in (Ti0.86Si0.14)N). The hardness is also retained after annealing at 900 oC for 2h.
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| 11. |
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| 12. |
- Sjölén, Jacob, et al.
(author)
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Oxynitride Coatings - Opportunities and Challenges from an Industrial Perspective
- 2011
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Conference paper (other academic/artistic)abstract
- The development of wear resistant coatings produced by different PVD techniques has mainly been focused onmetal-nitride and metal-carbide coatings, such as (Ti,Al)N, (Cr,Al)N, Ti(C,N) and (Ti,Si)N etc. However, duringthe recent years there has been a tremendous progress in the attempts to produce crystalline metal-oxide coatings,such as (Cr,Al)2O3, especially by using cathodic arc evaporation. Challenges, such as target poisoning andinsulating anodes have been overcome, opening up for a completely new group of materials. By the combinationof nitride and oxide coating processes, a new dimension in the material space has been opened, giving us metaloxy-nitrides. This presentation concerns coatings such as (Ti,Al)(O,N) and (Cr,Al)(O,N) deposited onto WC-Cosubstratesusing cathodic arc evaporation. Results for coating structure, analyzed by SEM, XRD, TEM, etc., andmechanical properties, analyzed by nanoindentation and metal cutting tests will be presented as a function of theO/N ratio. A unique advantage of the highly ionized plasmas combined with the relatively low depositiontemperatures in the cathodic arc processes is that the energy of the impinging species cause collision cascades inthe lattice that makes it possible to quench solid solutions and metastable compounds. These coatings have shownimproved metal cutting performance with enhanced tool life in both turning and milling applications.
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| 13. |
- Sjölén, Jacob, et al.
(author)
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Structure and mechanical properties of arc evaporated Ti–Al–O–N thin films
- 2007
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In: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 201:14, s. 6392-6403
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Journal article (peer-reviewed)abstract
- The structure, mechanical properties, and machining performance of arc evaporated Ti–Al–O–N coatings have been investigated for an Al0.66Ti0.34 target composition and O2/(O2+N2) gas flow-ratio varied between 0 to 24%. The coating structure was analysed using SEM, EDX, XRD, XPS, TEM, and STEM. Mechanical properties were analysed using nanoindentation and the deformation behaviour was analysed by probing the nanoindentation craters. The coatings performances in cutting tests were evaluated in a turning application in low carbon steel (DIN Ck45). It is shown that the addition of oxygen into the arc deposition process leads to the formation of a dual layer structure. It consists of an initial cubic NaCl-structure solid solution phase formed closest to the substrate, containing up to 35 at.% oxygen (O/O+N), followed by steady-state growth of a nanocomposite compound layer comprised of Al2O3, AlN, TiN, and Ti(O,N). The addition of oxygen increases the ductility of the coatings, which improves the performances in cutting tests. At high levels of oxygen, (>13 at.%), however, the performance is dramaticallyreduced as a result of increased crater wear.
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