| 1. |
- Broering Chaar, Ana Beatriz, 1990-, et al.
(författare)
-
The Effect of Cathodic Arc Guiding Magnetic Field on the Growth of (Ti0.36Al0.64)N Coatings
- 2019
-
Ingår i: Coatings. - : MDPI. - 2079-6412. ; 9:10
-
Tidskriftsartikel (refereegranskat)abstract
- We use a modified cathodic arc deposition technique, including an electromagnetic coil that introduces a magnetic field in the vicinity of the source, to study its influence on the growth of (Ti0.36Al0.64)N coatings. By increasing the strength of the magnetic field produced by the coil, the cathode arc spots are steered toward the edge of the cathode, and the electrons are guided to an annular anode surrounding the cathode. As a result, the plasma density between the cathode and substrate decreased, which was observed as a lateral spread of the plasma plume, and a reduction of the deposition rate. Optical emission spectroscopy shows reduced intensities of all recorded plasma species when the magnetic field is increased due to a lower number of collisions resulting in excitation. We note a charge-to-mass ratio decrease of 12% when the magnetic field is increased, which is likely caused by a reduced degree of gas phase ionization, mainly through a decrease in N2 ionization. (Ti0.36Al0.64)N coatings grown at different plasma densities show considerable variations in grain size and phase composition. Two growth modes were identified, resulting in coatings with (i) a fine-grained glassy cubic and wurtzite phase mixture when deposited with a weak magnetic field, and (ii) a coarse-grained columnar cubic phase with a strong magnetic field. The latter conditions result in lower energy flux to the coating’s growth front, which suppresses surface diffusion and favors the formation of c-(Ti,Al)N solid solutions over phase segregated c-TiN and w-AlN.
|
|
| 2. |
- Hsu, Tun-Wei, 1991-, et al.
(författare)
-
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
-
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.
|
|
| 3. |
- Hsu, Tun-Wei, 1991-
(författare)
-
Effect of metal ion irradiation on hard coating synthesis by physical vapor deposition
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to understand and control how the ions in the plasma influence the film growth during thin film deposition processes. Two physical vapor deposition (PVD) techniques are investigated, namely magnetron sputtering and cathodic arc evaporation. For magnetron sputtering, the unconventional hybrid high-power impulse and direct current magnetron cosputtering (HiPIMS/DCMS) configuration is used in this work. By synchronizing the substrate bias pulses with the HiPIMS pulses by a time offset and duration, the metal ions from the target material can be selected to impinge the growing film, whereas the contribution of the working gas ions can be effectively reduced. Two aspects are explored, low-mass ion subplantation and heavy-mass ion irradiation.The thesis begins with establishing the correlation between N2 pressure and plasma properties of the cathodic arc evaporation process using Ti0.5Al0.5 target. The results show Ti ions are the dominant species, followed by Al+. On the other hand, due to the shorter mean free path of the species with increasing N2 pressure, the ion energies and the effective electron temperature decrease while electron density increases. Consequently, comparing the TiAlN coatings grown at lower and higher N2 pressures, the crystallographic textures changes from cubic 220 to 111 along the growth direction, and the residual stress reduces from compressive (-3.4 GPa) to almost stress-free (0.6 GPa).The rest of the thesis addresses the influence of ionized species on microstructures, with a focus on tuning film properties by ions in the plasma. Ti1-x(AlySi1-y)xN coatings (0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00) were deposited with an AlSi-HiPIMS/Ti-DCMS with synchronized substrate bias setup. The results show that the coatings deposited by this method have higher Al and Si solubilities in NaCl-structured TiN than other PVD techniques due to low mass ion subplantations. Additionally, a range of films with different compositions display a combination of high hardness (~ 30 GPa) and low residual stress (s < 0.5 GPa), which highlights the benefits of minimizing the Ar+ incorporation by synchronizing substrate bias to the Al+/Si+-rich portion of the HiPIMS pulses. The selected TiAlSiN coatings were then studied for the crater wear resistance of high-speed cutting performance on ball bearing steel (100Cr6). The effects of phase contents and microstructures on cutting performance are evaluated.This is further extended by a study of the influence of neutral and ion fluxes overlap and the subplantation range of low-mass ions. This is accomplished by introducing the 1-fold substrate table rotation, different target-to-substrate distances, and substrate bias voltage in a AlSi-HiPIMS/Ti-DCMS hybrid deposition process. The microstructure and phase analysis show the necessity of overlap between HiPIMS and DCMS fluxes to deposit TiAlSiN solid solutions. The compositional variation of the multilayers can be controlled by the applied substrate bias and table rotational speed. Rotation during deposition may yield coatings comparable in hardness to the ones without rotation at the expense of higher compressive stress.The effectiveness of controlling heavy ion irradiation is investigated by replacing external heating with high-mass W+ irradiation to grow dense and hard titanium tungsten carbide (TiWC) coatings by WC-HiPIMS/TiC-DCMS with synchronized bias technique. The ionization degree of W+ are controlled by the peak current density (0.27 ≤ JT ≤ 1.36 A/cm2). The results show that W+ irradiation effectively densified TiWC coatings without external heating. The total energy consumption per hour is reduced by 77% using the HiPIMS/DCMS setup without external heating, yet this TiWC coating is 10 GPa harder than similar coating grown by self-bias DCMS with heating.
|
|
| 4. |
- Hsu, Tun-Wei, 1991-, et al.
(författare)
-
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.
|
|
| 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
-
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.
|
|
| 6. |
- Salamania, Janella, 1992-, et al.
(författare)
-
Elucidating dislocation core structures in titanium nitride through high-resolution imaging and atomistic simulations
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterizedthin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. Byhigh-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besidesthe expected primary a/2{110}h110i dislocation, Shockley partial dislocations a/6{111}h112i and sessileLomer edge dislocations a/2{100}h011i. Density-functional theory and classical interatomic potentialsimulations complement STEM observations by recovering the atomic structure of the different disloca-tion types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core.The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakenedTi-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}h110i and {111}h112idislocations. Our findings underscore that the presence of different dislocation types and their effects onchemical bonding should be considered in the design and interpretations of nanoscale and macroscopicproperties of TiN.
|
|
