| 1. |
- Bahr, Ahmed, et al.
(författare)
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Quaternary diborides-improving the oxidation resistance of TiB2 +/- z coatings by disilicide alloying
- 2023
-
Ingår i: Materials Research Letters. - : Informa UK Limited. - 2166-3831. ; 11:9, s. 733-741
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Tidskriftsartikel (refereegranskat)abstract
- To overcome the limited oxidation resistance of the emerging class of transition metal borides, we suggest within this study novel quaternary diborides, Ti-TM-Si-B-2 +/- z (TM = Ta, Mo), achieving the compromise between excellent oxidation resistance and requirements of hard coatings. Single-phase AlB2-type structured Ti-TM-Si-B-2 +/- z films (3-5 mu m) are sputter-deposited from TiB2/TMSi2 targets. The Ti-Ta-Si-B-2 +/- z coatings exhibit 36 GPa in hardness, while maintaining strongly retarded oxidation kinetics till 1000 degrees C. Ti-Mo-Si-B-2 +/- z coatings preserve a hardness up to 27 GPa, although outperforming all their counterparts by featuring outstanding oxidation resistance with 440nm oxide scale thickness after 1 h at 1200 degrees C. First report on quaternary Ti-TM-Si-B-2 +/- z coatings stabilized in hexagonal AlB2-prototype structures. These hard coating materials exhibit unprecedented oxidation resistance up to 1200 degrees C due to the formation of Si-rich scales.
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| 2. |
- Chien, Yu-Ping, et al.
(författare)
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Deviations between film and target compositions induced by backscattered Ar during sputtering from M-2-Al-C (M = Cr, Zr, and Hf) composite targets
- 2022
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 446
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Tidskriftsartikel (refereegranskat)abstract
- M-Al-C (M = Cr, Zr, and Hf) thin films are deposited from stoichiometric M2AlC composite targets by direct current magnetron sputtering (DCMS) and high power pulsed magnetron sputtering (HPPMS) in an industrial coater. Using DCMS it is observed that the composition of the Cr-Al-C film is close to stoichiometric, while the Al concentration in the Zr-Al-C and Hf-Al-C films is significantly reduced compared to the Al concentration in the targets. It is evident that the magnitude of the difference in Al concentration between the target and the cor-responding film composition is strongly dependent on the atomic mass of the transition metal. Zr and Hf atoms are 1.8 and 3.4 times heavier than Cr. In HPPMS, the target potential is approximately 1.6 times larger than that in DCMS, which can result in the film compositions deviating even stronger from the target composition as compared to DCMS. The Zr-Al-C thin film deposited by HPPMS exhibits a larger Al-deficiency than the film deposited by DCMS. The energy distributions of backscattered Ar neutrals are simulated by utilizing a two-body collision model and the Transport of Ions in Matter (TRIM) code. Based on the simulation results the experimentally observed Al -deficient film compositions can be readily explained: As the mass of the transition metal in the target is increased, both, energy and flux of the (at the target) reflected Ar is increased causing preferential re-sputtering of Al in the films. As stoichiometric compositions are a prerequisite for the formation of single-phase compound thin films it is evident that composite targets with a transition metal mass-dependent Al-overstoichiometry are required to compensate the Al-loss induced by the energetic Ar neutrals.
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| 3. |
- Hsu, Tun-Wei, 1991-, et al.
(författare)
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Dense and hard TiWC protective coatings grown with tungsten ion irradiation using WC-HiPIMS/TiC-DCMS co-sputtering technique without external heating
- 2023
-
Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 618
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Tidskriftsartikel (refereegranskat)abstract
- Titanium tungsten carbide (TiWC) coatings are deposited by a combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique. No external heating is applied during deposition phase, instead, the thermally driven adatom mobility is substituted by heavy ion irradiation. DCMS sources equipped with titanium carbide targets provide constant neutral fluxes to establish the predominant coating structures, whereas tungsten carbide target in HiPIMS mode serves as the source of heavy metal-ions. Substrate bias of −60 V is synchronized to W+ ion-rich time domains of HiPIMS pulses to minimize the contribution from working gas ions. The influence of W+ ion flux intensity, controlled by varying peak target current density (JT), on film properties is investigated. X-ray photoelectron spectroscopy reveals the presence of over stoichiometric carbon forming an amorphous phase, the amount of which can be fine-tuned by varying JT. Changes in film composition as a function of JT are explained based on the in-situ ion mass spectroscopy analyses. Dense TiWC coatings by hybrid process exhibit hardness higher than 30 GPa, which are comparable to TiWC films deposited by DCMS with dc substrate bias and external heating. The relative energy consumption in the hybrid process is reduced by 77 % as compared to high-temperature DCMS processing.
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| 4. |
- Hsu, Tun-Wei, 1991-, et al.
(författare)
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Effects of substrate rotation during AlSi-HiPIMS/Ti-DCMS co-sputtering growth of TiAlSiN coatings on phase content, microstructure, and mechanical properties
- 2023
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 453
-
Tidskriftsartikel (refereegranskat)abstract
- A combined high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) technique is used to deposit Ti0.6Al0.32Si0.08N films with 1-fold substrate table rotation. Layers are grown at two different substrate-target separations, two different rotational speeds, and with different values of substrate bias. The aim is to study the role of (1) overlap between ion and neutral fluxes generated from HiPIMS and DCMS sources, respectively, and (2) the subplantation range of low-mass ions. Results from X-ray diffractometry highlight the necessity of flux intermixing in the formation of the metastable B1-structured TiAlSiN solid solutions. All films grown at short target-to-substrate distance contain the hexagonal AlN phase, as there is essentially no overlap between HiPIMS and DCMS fluxes, thus the Al+ and Si+ subplantation is very limited. Under conditions of high flux intermixing corresponding to larger target-to-substrate distance, no w-AlN forms irrespective of rotational speed (1 or 3 rpm) and bias amplitude (120 or 480 V), indicating that the role of Al+/Si+ and Ti flux overlap is crucial for the phase formation during film growth by HiPIMS/DCMS with substrate rotation. This conclusion is further supported by the fact that the reduction of the bilayer thickness with increasing the target-to-substrate distance (hence increasing flux overlap) is larger for films grown with higher amplitude of the substrate bias, indicative of more efficient Al+/Si+ subplantation into the c-TiN phase. Single-phase films with the hardness close to that of layers grown with stationary substrate table can be achieved, however, at the expense of higher compressive stress.
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| 5. |
- Hsu, Tun-Wei, 1991-, et al.
(författare)
-
Influence of Si content on phase stability and mechanical properties of TiAlSiN films grown by AlSi-HiPIMS/Ti-DCMS co-sputtering
- 2021
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 427
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Tidskriftsartikel (refereegranskat)abstract
- Ti1-x(AlySi1-y)xN coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al+/Si+ ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al+/Si+-rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al1.0Si0.0, Al0.9Si0.1, Al0.8Si0.2, and Al0.6Si0.4. X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiNz rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~ 30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than -3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~ 30 GPa) and low residual stress (σ < 0.5 GPa). Such an unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al+/Si+ supplantation effect and minimizes the Ar+ incorporation.
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| 6. |
- Janknecht, Rebecca, et al.
(författare)
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A Strategy to Enhance the B-Solubility and Mechanical Properties of Ti-B-N Thin Films
- 2024
-
Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 271
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Tidskriftsartikel (refereegranskat)abstract
- The Ti–B–N system offers a wide range of possible meta(stable) phases, making it interesting for science and industry. However, the solubility for B within the face-centered cubic (fcc)-TiN lattice is rather limited and less studied, especially without forming B-rich phases. Therefore, we address how chemistries along the TiN–TiB2 or TiN–TiB tie-line influence this B-solubility. The variation between these two tie-lines is realized through non-reactive co-sputtering of a TiN, TiB2, and Ti target. We show that for variations along the TiN–TiB tie-line, even 8.9 at.% B (equivalent to 19.3 at.% non-metal fractions) can fully be incorporated into the fcc-TiNy lattice without forming other B-containing phases. The combination of detailed microstructural characterization through X-ray diffraction and transmission electron microscopy with ab initio calculations of fcc-Ti1-xNBx, fcc-TiN1-xBx, and fcc-TiN1-2xBx solid solutions indicates that B essentially substitutes N.The single-phase fcc-TiB0.17N0.69 (the highest B-containing sample along the TiN–TiB tie-line studied) exhibits the highest hardness H of 37.1±1.9 GPa combined with the highest fracture toughness KIC of 3.0±0.2 MPa·m1/2 among the samples studied. These are markedly above those of B-free TiN0.87 having H = 29.2±2.1 GPa and KIC = 2.7±<0.1 MPa·m1/2.
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| 7. |
- Nedfors, Nils, et al.
(författare)
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Influence of the Al concentration in Ti-Al-B coatings on microstructure and mechanical properties using combinatorial sputtering from a segmented TiB2/AlB2 target
- 2019
-
Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 364, s. 89-98
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Tidskriftsartikel (refereegranskat)abstract
- A series of (TixAl1-x)B2 +y coatings with compositions in the range of x = 0.01-0.94 and y = 1.70-2.92 has been synthesized using magnetron sputtering from a segmented TiB2/AlB2 target. The coatings are amorphous at x amp;lt;= 0.05 while a (TixAl1-x)B2+y solid solution forms for x amp;gt; 0.05. As a consequence of the sputtering process, the B/(Ti + Al) atomic ratio varied with the metal content resulting in the formation of under-stoichiometric coatings at x amp;lt; 0.35 and over-stoichiometric coatings at x amp;gt; 0.35. Surplus Al segregates to grain boundaries of the under-stoichiometric coatings whereas the over-stoichiometric coatings have a tissue phase containing mainly B and some Al. The B-rich tissue phase restrains grain growth in the in-plane direction while an increase in Ti content promotes the growth of columnar structured coatings with a pronounced (001) texture up to x = 0.84. The combination of such preferred orientation and tissue phase results in the highest hardness of 39 GPa for the (Ti0.79Al0.21)B-2.70 coating. The Youngs modulus, on the other hand, increases continuously from 262 GPa for the most Al-rich coating to 478 GPa for the most Ti-rich coating. Comparing to calculated values of Youngs modulus, good agreement is observed for the close to stoichiometric coatings (x = 0.40-0.50). For the off-stoichiometric coatings, the experimental values are lower due to the existence of the tissue phase.
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| 8. |
- Schmid, Barbara, et al.
(författare)
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Mechanical properties of VC/ZrC and VC/HfC superlattices
- 2024
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- Face -centered cubic transition metal carbides exhibit high melting points and hardness, making them prominent candidates for protective coating applications. Vanadium carbide (VC) has typical characteristics of transition metal carbides. It serves as model material in this study, in which we showcase the effect of superlattice architecture on mechanical properties and fracture toughness. While beneficial effects of superlattice arrangement have been demonstrated for a series of nitride -based coatings, transition metal carbides remain largely unexplored territory. Following density functional theory based ab initio predictions on lattice and shear modulus mismatch, we develop VC/ZrC and VC/HfC superlattice coatings synthesized via pulsed DC sputter deposition. The bilayer periods ( Lambda ) of our fully fcc-structured polycrystalline coatings range between 2 - 50 nm (indicated by X-ray diffraction, transmission and scanning electron microscopy). The chemical composition is close to 1:1 stoichiometry (from X-ray fluorescence, elastic back -scattering spectrometry and elastic recoil detection analysis). Both superlattice series exhibit a strong dependence of hardness, elastic modulus, and fracture toughness on their bilayer periods, which can only be correlated with the in -plane stress variations for VC/ZrC. The VC/HfC superlattices provide their peak -hardness of 36.0 +/- 1.6 GPa for Lambda = 6 nm and their peak in fracture toughness of 3.5 +/- 0.5 MPa root m for Lambda = 10 nm.
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| 9. |
- Syed, Bilal, 1977-, et al.
(författare)
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Effect of work function and cohesive energy of the constituent phases of Ti-50 at.% Al cathode during arc deposition of Ti-Al-N coatings
- 2019
-
Ingår i: Surface & Coatings Technology. - USA : Elsevier. - 0257-8972 .- 1879-3347. ; 357, s. 393-401
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Tidskriftsartikel (refereegranskat)abstract
- The differences in work function (W.F.) and cohesive energy (C.E.) of the phases constituting the cathode, plays an important role in the formation of the converted layer at its near-surface region during cathodic arc deposition. As a consequence, this also affects the deposition conditions for the coatings. In this study, we explore the effect of W.F. and C.E. of the constituent phases during arc evaporation by utilizing two kinds of customized Ti-50 at.% Al cathodes with different phase compositions. Our results show that during reactive arc evaporation the disparity in W.F. and C.E. among the constituent phases of Ti-50 at.% Al cathodes leads to preferential erosion of the phases with lower W.F. and C.E. The aforementioned preferential erosion begets higher surface roughness on the Ti-50 at.% Al cathode with a wider range of W.F. and C.E. disparity. It is also observed that the thermal conductivity of the Ti-50 at.% Al cathode plays a dominant role in the deposition rate of Ti-Al-N coating. This article also presents how the surface geometry of the cathode in the presence of arc guiding magnetic field significantly influences the microstructure of the deposited coatings.
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| 10. |
- Syed, Bilal, et al.
(författare)
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Morphology and microstructure evolution of Ti-50 at.% Al cathodes during cathodic arc deposition of Ti-Al-N coatings
- 2017
-
Ingår i: Journal of Applied Physics. - Melville, New York 11747-4300 : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 121:24
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Tidskriftsartikel (refereegranskat)abstract
- Today's research on the cathodic arc deposition technique and coatings therefrom primarily focuses on the effects of, e.g., nitrogen partial pressure, growth temperature, and substrate bias. Detailed studies on the morphology and structure of the starting material—the cathode—during film growth and its influence on coating properties at different process conditions are rare. This work aims to study the evolution of the converted layer, its morphology, and microstructure, as a function of the cathode material grain size during deposition of Ti-Al-N coatings. The coatings were reactively grown in pure N2discharges from powder metallurgically manufactured Ti-50 at.% Al cathodes with grain size distribution averages close to 1800, 100, 50, and 10 μm, respectively, and characterized with respect to microstructure, composition, and mechanical properties. The results indicate that for the cathode of 1800 μm grain size the disparity in the work function among parent phases plays a dominant role in the pronounced erosion of Al, which yields the coatings rich in macro-particles and of high Al content. We further observed that a reduction in the grain size of Ti-50 at.% Al cathodes to 10 μm provides favorable conditions for self-sustaining reactions between Ti and Al phases upon arcing to form γ phase. The combination of self-sustaining reaction and the arc process not only result in the formation of hole-like and sub-hole features on the converted layer but also generate coatings of high Al content and laden with macro-particles.
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| 11. |
- Thörnberg, Jimmy, et al.
(författare)
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Oxidation resistance and mechanical properties of sputter-deposited Ti0.9Al0.1B2-y thin films
- 2022
-
Ingår i: Surface & Coatings Technology. - : Elsevier Science SA. - 0257-8972 .- 1879-3347. ; 442
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Tidskriftsartikel (refereegranskat)abstract
- Direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) were used to deposit understoichiometric Ti(1-x)Al(x)B(2-y )diboride coatings by sputtering from a segmented TiB2-AlB2 target using Ar and Kr as sputtering gas. For films with a fixed Al/(Ti + Al) ratio of x = 0.1 (Ti0.9Al0.1B2-y), the B content was varied with y & ISIN; (0.1, 0.6 and 0.7). For films with a fixed y = 0.7 (Ti1-xAlxB1.3), the Al content was varied with x & ISIN; (0.1, 0.4 and 0.7). Evaluation of the mechanical properties of the Ti1-xAlxB1.3 samples showed a reduction in both hardness and elastic modulus with increasing Al concentration, while the Ti0.9Al0.1B2-y samples showed a hardness increase with decreasing B content. Thus, Ti0.9Al0.1B1.3 films exhibited a superior hardness of 46.2 +/- 1.1 GPa and an elastic modulus of 523 & PLUSMN; 7 GPa, compared to the values for Ti0.9Al0.1B1.4 and Ti0.9Al0.1B1.9, showing a hardness of 44 +/- 1 GPa and 36 +/- 1 GPa, and an elastic modulus of 569 +/- 7 GPa and 493 +/- 6 GPa, respectively. The oxidation behavior of the mechanically most promising Ti0.9Al0.1B2-y sample series was investigated through air-annealing at 600 C for durations from 1 h to 10 h. All films formed a mixed non-conformal Al2O3-TiO2 oxide scale which acts as an inward and outward diffusion barrier, significantly reducing the oxidation rate compared to TiBz films, which form an oxide scale consisting of porous TiO2. The thinnest oxide scale after 10 h was found in the B-deficient samples, Ti0.9Al0.1B1.3 and Ti0.9Al0.1B1.4, at ~200 nm, which is significantly below that for Ti0.9Al0.1B1.9 at 320 nm. The enhanced oxidation resistance of highly understoichiometric films is due to the elimination of the B-rich tissue phase that is present at the grain boundaries for higher B content, where the latter has been shown to enhance the rate of oxidation in borides.
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| 12. |
- Zendejas Medina, León, et al.
(författare)
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Enhancing corrosion resistance, hardness, and crack resistance in magnetron sputtered high entropy CoCrFeMnNi coatings by adding carbon
- 2021
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- This study explores carbon addition as a materials design approach for simultaneously improving the hardness, crack resistance, and corrosion resistance of high entropy thin films. CoCrFeMnNi was selected as a starting point, due to its high concentration of weak carbide formers. The suppression of carbides is crucial to the approach, as carbide formation can decrease both ductility and corrosion resistance. Films with 0, 6, and 11 at.% C were deposited by magnetron co-sputtering, using a graphite target and a sintered compound target. The samples with 0 at.% C crystallized with a mixture of a cubic closed packed (ccp) phase and the intermetallic chi-phase. With 6 and 11 at.% C, the films were amorphous and homogenous down to the nm-scale. The hardness of the films increased from 8 GPa in the carbon-free film to 16 GPa in the film with 11 at.% C. Furthermore, the carbon significantly improved the crack resistance as shown in fragmentation tests, where the crack density was strongly reduced. The changes in mechanical properties were primarily attributed to the shift from crystalline to amorphous. Lastly, the carbon improved the corrosion resistance by a progressive lowering of the corrosion current and the passive current with increasing carbon concentration.
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| 13. |
- Zhirkov, Igor, et al.
(författare)
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A comparison of plasma generation, plasma transport, and film formation for a DC vacuum arc source with Ti-X compound cathodes (X = W, C, Al, and Si)
- 2023
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 133:23
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Tidskriftsartikel (refereegranskat)abstract
- This investigation reports the influence of Ti-C and Ti-W cathode composition on an industrial-scale dc vacuum arc plasma source. Further, we analyze the influence of plasma generation and plasma properties on the resulting cathode surface after the operation and on basic film properties. The results are compared with previous work focused on Ti-Al and Ti-Si compound cathodes. For all Ti-X compound cathodes (X = W, C, Al, and Si), a direct correlation between plasma ion energy/charge and the cohesive energy of the cathode was demonstrated, with a small number of exceptions to a limited set of specific cathode compositions. Hence, the "velocity rule" and effects from different electron temperatures were suggested to be important for gaining a more detailed understanding of plasma properties. A discrepancy was found between the cathode and plasma ion composition, though the difference was reduced in a corresponding comparison between the cathode and the deposited film composition. A significant contribution of a flux of neutrals and/or macroparticles to the final film composition was, therefore, suggested. The effect of the melting point of the cathode phase composition on the intensity of macroparticle generation and the smoothness of the cathode surface operation was also investigated. The presented results contribute to the fundamental understanding of vacuum arc plasma generation and transport and are of importance for further development and applicability of Ti-based coatings from arc deposition.
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| 14. |
- Zhirkov, Igor, et al.
(författare)
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Effect of Mo-Cu cathode composition on process stability, macroparticle formation, plasma generation, and thin-film deposition in DC arc synthesis
- 2020
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 127:1
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present the correlation between cathode composition and features of the arcing process for Mo1-xCux [x = 0.0, 0.07 (0.05), 0.14 (0.10), 0.21 (0.15), 0.40 (0.3), 0.73 (0.63), 0.97 (0.95), and 1.00, atomic fraction (weight fraction)] cathodes used in a DC vacuum-arc deposition system. It is found that the stability of the arcing process crucially depends on the cathode composition. The most stable arc spot and the lowest cathode potential (similar to 19 V) are detected for the Mo0.27Cu0.73 cathode, while the Mo0.93Cu0.07 cathode shows the most unstable arcing process with the highest cathode potential (similar to 28 V). The properties of the generated plasma are also strongly dependent on the relative ratio of the cathode elements. The metal ions from the Mo and Cu cathodes have peak kinetic energies around 136 and 62 eV, respectively, while for a Mo0.79Cu0.21 cathode, the corresponding energies are only 45 and 28 eV. The average charge states decreased from 2.1 to 1.6 for Mo ions and from 2 to 1.2 for Cu ions. The intensity of macroparticle generation and the size of the droplets correlate with the relative fraction of Cu. However, it is shown that, typically for the cathodes with a low amount of Cu, an increased abundance of visually observed macroparticles leads to droplet-free films. The film thicknesses and their compositions also demonstrate dependencies on the elemental composition of the cathode. These results are discussed in the light of no solubility between Mo and Cu and the high temperature of the cathode surface during the arcing process. Published under license by AIP Publishing.
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| 15. |
- Zhirkov, Igor, et al.
(författare)
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Effect of Ti-Al cathode grain size on plasma generation and thin film synthesis from a direct current vacuum arc plasma source
- 2019
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Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we investigate the influence of powder metallurgical manufactured Ti0.5Al0.5 cathode grain size (45-150 mu m) on the properties of a DC arc discharge, for N-2 pressures in the range 10(-5) Torr (base pressure) up to 3x10(-2) Torr. Intermetallic TiAl cathodes are also studied. The arc plasma is characterized with respect to ion composition, ion charge state, and ion energy, and is found to change with pressure, independent on choice of cathode. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the cathode surfaces and the concurrently deposited films are used for exploring the correlation between cathode-, plasma-, and film composition. The plasma has a dominating Al ion content at elevated pressures, while the film composition is consistent with the cathode composition, independent on cathode grain size. Cross-sections of the used cathodes are studied, and presence of a converted layer, up to 10 mu m, is shown, with an improved intermixing of the elements on the cathode surface. This layer is primarily explained by condensation of cathode material from the melting and splashes accompanying the arc spot movement, as well as generated plasma ions being redeposited upon returning to the cathode. The overall lack of dependence on grain size is likely due to similar physical properties of Ti, Al and TiAl grains, as well as the formation of a converted layer. The presented findings are of importance for large scale manufacturing and usage of Ti-Al cathodes in industrial processes. (C) 2019 Author(s).
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| 16. |
- Zhirkov, Igor, et al.
(författare)
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Generation of super-size macroparticles in a direct current vacuum arc discharge from a Mo-Cu cathode
- 2016
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 108:5, s. 054103-
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Tidskriftsartikel (refereegranskat)abstract
- An inherent property of cathodic arc is the generation of macroparticles, of a typical size ranging from submicrometer up to a few tens of mu m. In this work, we have studied macroparticle generation from a Mo0.78Cu0.22 cathode used in a dc vacuum arc discharge, and we present evidence for super-size macroparticles of up to 0.7mm in diameter. All analyzed particles are found to be rich in Mo (>= 98 at. %). The particle generation is studied by visual observation of the cathode surface during arcing, by analysis of composition and geometrical features of the used cathode surface, and by examination of the generated macroparticles with respect to shape and composition. A mechanism for super-size macroparticle generation is suggested based on observed segregated layers of Mo and Cu identified in the topmost part of the cathode surface, likely due to the discrepancy in melting and evaporation temperatures of Mo and Cu. The results are of importance for increasing the fundamental understanding of macroparticle generation, which in turn may lead to increased process control and potentially provide paths for tuning, or even mitigating, macroparticle generation. (C) 2016 AIP Publishing LLC.
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| 17. |
- Zhirkov, Igor, et al.
(författare)
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Macroparticle generation in DC arc discharge from a WC cathode
- 2017
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:10
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Tidskriftsartikel (refereegranskat)abstract
- We have studied macroparticle generation from a tungsten carbide cathode used in a dc vacuum arc discharge. Despite a relatively high decomposition/ melting point (similar to 3100 K), there is an intensive generation of visible particles with sizes in the range 20-35 mu m. Visual observations during the discharge and scanning electron microscopy of the cathode surface and of collected macroparticles indicate a new mechanism for particle formation and acceleration. Based on the W-C phase diagram, there is an intensive sublimation of carbon from the melt resulting from the cathode spot. The sublimation supports the formation of a sphere, which is accelerated upon an explosion initiated by Joule heating at the critical contact area between the sphere and the cathode body. The explosive nature of the particle acceleration is confirmed by surface features resembling the remains of a splash on the droplet surface. Published by AIP Publishing.
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| 18. |
- Zhirkov, Igor, et al.
(författare)
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Process development for stabilization of vacuum arc plasma generation from a TiB2 cathode
- 2019
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Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we present stable and reproducible arc plasma generation from a TiB2 cathode. The process development contains three complimentary features: Use of a Mo cylinder around the TiB2 cathode improves arc ignition and stabilizes the process by keeping the arc spot at the cathode surface. The evolution of the cathode surface during erosion and the process stability is further improved by addition of 1wt% carbon in the cathode, with no resulting change in plasma characteristics (ion energy, ion charge states, macroparticles). Finally, an increased plasma density through use of a separate anode provides the last key point, which together with the other two contributes to highly controlled plasma generation from TiB2 using DC vacuum arc, and complete utilization of the cathode material. The combined results provide a novel and efficient route for synthesis of metal borides. (C) 2019 Author(s).
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| 19. |
- Zhirkov, Igor, et al.
(författare)
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Stable DC vacuum arc plasma generation from a 100 mm TiB2 cathode
- 2024
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 484
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Tidskriftsartikel (refereegranskat)abstract
- Titanium diboride exhibits outstanding properties for hard and wear resistant coatings. However, efficient physical vapor deposition (PVD) processing through DC vacuum arc, with a deposition rate unreachable for any other PVD technique, is comparatively unexplored for TiB2 thin films due to challenges associated with the film synthesis process. In this work, we used an industrial scale arc plasma source having a plane cathode of 100 mm in diameter and a permanent magnet on its back side. We present analysis of the cathode surface, plasma generation/composition, as well as analysis of collected macroparticles. The cathode weight loss and the amount of generated macroparticles were measured as a function of process parameters (arc current and pressure, in both Ar and N2 gas). Plasma analysis shows average ion energies around 120 and 25 eV for Ti and B, respectively, and plasma ion composition of approximately 50 % Ti and 50 % B. The cathode weight loss was around 0.3-0.5 g/ min, of which at least 25 % is estimated to be macroparticles. Notably, the intensity of the macroparticle generation was reduced with an increase in N2 pressure. Altogether, the results show a stable and reproducible plasma generation process and a high potential for the use of the cathodic arc as an efficient and useful method for deposition of metal borides.
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| 20. |
- Zhirkov, Igor, et al.
(författare)
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Vacuum arc plasma generation and thin film deposition from a TiB2 cathode
- 2015
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 107:18, s. 184103-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the utilization of TiB2 cathodes for thin film deposition in a DC vacuum arc system. We present a route for attaining a stable, reproducible, and fully ionized plasma flux of Ti and B by removal of the external magnetic field, which leads to dissipation of the vacuum arc discharge and an increased active surface area of the cathode. Applying a magnetic field resulted in instability and cracking, consistent with the previous reports. Plasma analysis shows average energies of 115 and 26 eV, average ion charge states of 2.1 and 1.1 for Ti and B, respectively, and a plasma ion composition of approximately 50% Ti and 50% B. This is consistent with measured resulting film composition from X-ray photoelectron spectroscopy, suggesting a negligible contribution of neutrals and macroparticles to the film growth. Also, despite the observations of macroparticle generation, the film surface is very smooth. These results are of importance for the utilization of cathodic arc as a method for synthesis of metal borides. (C) 2015 AIP Publishing LLC.
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