Special Issue "Microstructures and Mechanical Properties of Metallic Thin Films and Coatings"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Thin Films and Interfaces".

Deadline for manuscript submissions: 31 October 2021.

Special Issue Editor

Dr. Helmut Riedl
E-Mail Website1 Website2
Guest Editor
Institute of Materials Science and Technology, TU Wien, Vienna, Austria
Interests: surface engineering; PVD techniques; structure–property relationships; HR-characterization methods; atomistic modeling

Special Issue Information

Dear Colleagues,

As surface engineering is a steadily growing, interdisciplinary field, the application of thin films and coatings for enhancing specific properties of bulk materials is becoming highly popular. In particular, metallic coating materials are a hot topic as the usage ranges from fracture resistant metallic glasses in microelectronics to protective coatings against harsh environments, up to so-called smart layers in biomedical applications— to mention just a few examples. For all these versatile applications, an in-depth understanding of the microstructure and related properties is essential.

This Special Issue will focus on recent advances in the field of metallic coating materials and the relation between microstructural evolution and their mechanical properties. The Special Issue should be a platform for articles dealing with specific structure–property relationships of metallic coatings, their chemical compositions, and alloying concepts to enhance their thermomechanical properties; fracture resistance and related characterization techniques; mechanical properties such as residual stress, hardness, or indentation modulus in general; phase formation with respect to crystalline and amorphous structures; as well as high-resolution characterization (e.g., HR-TEM, ATP, or nanobeam experiments) techniques to gain insights on predominant phases. For this Special Issue, PVD-based deposition techniques are preferred though other techniques will be considered.

Dr. Helmut Riedl
Guest Editor

Manuscript Submission Information

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Keywords

  • metallic coating materials
  • mechanical properties
  • fracture resistant
  • PVD-based synthesis techniques
  • alloying concepts
  • phase formation
  • crystalline and amorphous structures

Published Papers (4 papers)

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Research

Open AccessArticle
Synthesis and Characterisation of Nanocomposite Mo-Fe-B Thin Films Deposited by Magnetron Sputtering
Materials 2021, 14(7), 1739; https://doi.org/10.3390/ma14071739 - 01 Apr 2021
Viewed by 272
Abstract
Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0–37 at.% using [...] Read more.
Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0–37 at.% using non-reactive DC (direct current) magnetron sputtering. The phase composition, microstructure, and mechanical properties were investigated using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation measurements. Films deposited at 300 °C and with >7 at.% Fe are nanocomposites consisting of two amorphous phases: a metal-rich phase and a metal-deficient phase. Hardness and elastic modulus were reduced with increasing Fe-content from ~29 to ~19 GPa and ~526 to ~353 GPa, respectively. These values result in H3/E2 ratios of 0.089–0.052 GPa, thereby indicating brittle behaviour of the films. Also, no indication of crystalline ternary phases was observed at temperatures up to 600 °C, suggesting that higher temperatures are required for such films to form. Full article
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Open AccessArticle
Fabrication and Mechanical Properties of Cr2AlC MAX Phase Coatings on TiBw/Ti6Al4V Composite Prepared by HiPIMS
Materials 2021, 14(4), 826; https://doi.org/10.3390/ma14040826 - 09 Feb 2021
Cited by 1 | Viewed by 637
Abstract
The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase [...] Read more.
The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic. Full article
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Open AccessArticle
Assessment of Technological Capabilities for Forming Al-C-B System Coatings on Steel Surfaces by Electrospark Alloying Method
Materials 2021, 14(4), 739; https://doi.org/10.3390/ma14040739 - 05 Feb 2021
Viewed by 547
Abstract
In this paper, the possibility of applying the electrospark alloying (ESA) method to obtain boron-containing coatings characterised by increased hardness and wear resistance is considered. A new method for producing such coatings is proposed. The method consists in applying grease containing aluminium powder [...] Read more.
In this paper, the possibility of applying the electrospark alloying (ESA) method to obtain boron-containing coatings characterised by increased hardness and wear resistance is considered. A new method for producing such coatings is proposed. The method consists in applying grease containing aluminium powder and amorphous boron to the surface to be treated and subsequently processing the obtained surface using the ESA method by a graphite electrode. The microstructural analysis of the Al-C-B coatings on steel C40 showed that the surface layer consists of several zones, the number and parameters of which are determined by the energy conditions of the ESA process. Durametric studies showed that with an increase in the discharge energy influence, the microhardness values of both the upper strengthened layer and the diffusion zone increased to Wp = 0.13 J, Hµ = 6487 MPa, and Wp = 4.9 J, Hµ = 12350 MPa, respectively. The results of X-ray diffraction analysis indicate that at the discharge energies of 0.13 and 0.55 J, the phase composition of the coating is represented by solid solutions of body-centred cubic lattice (BCC) and face-centred cubic lattice (FCC). The coatings obtained at Wp = 4.9 J were characterised by the presence of intermetallics Fe4Al13 and borocementite Fe3 (CB) in addition to the solid solutions. The X-ray spectral analysis of the obtained coatings indicated that during the electrospark alloying process, the surface layers were saturated with aluminium, boron, and carbon. With increasing discharge energy, the diffusion zone increases; during the ESA process with the use of the discharge energy of 0.13 J for steel C40, the diffusion zone is 10–15 μm. When replacing a substrate made of steel C40 with the same one material but of steel C22, an increase in the thickness of the surface layer accompanied by a slight decrease in microhardness is observed as a result of processing with the use of the ESA method. There were simulated phase portraits of the Al-C-B coatings. It is shown that near the stationary points in the phase portraits, one can see either a slowing down of the evolution or a spiral twisting of the diffusion-process particle. Full article
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Open AccessArticle
Kinetically Limited Phase Formation of Pt-Ir Based Compositionally Complex Thin Films
Materials 2020, 13(10), 2298; https://doi.org/10.3390/ma13102298 - 16 May 2020
Viewed by 758
Abstract
The phase formation of PtIrCuAuX (X = Ag, Pd) compositionally complex thin films is investigated to critically appraise the criteria employed to predict the formation of high entropy alloys. The formation of a single-phase high entropy alloy is predicted if the following requirements [...] Read more.
The phase formation of PtIrCuAuX (X = Ag, Pd) compositionally complex thin films is investigated to critically appraise the criteria employed to predict the formation of high entropy alloys. The formation of a single-phase high entropy alloy is predicted if the following requirements are fulfilled: 12 J∙K−1 mol−1 ≤ configurational entropy ≤ 17.5 J∙K−1 mol−1, −10 kJ∙mol−1 ≤ enthalpy of mixing ≤ 5 kJ∙mol−1 and atomic size difference ≤ 5%. Equiatomic PtIrCuAuX (X = Ag, Pd) fulfill all of these requirements. Based on X-ray diffraction and energy-dispersive X-ray spectroscopy data, near-equiatomic Pt22Ir23Cu18Au18Pd19 thin films form a single-phase solid solution while near-equiatomic Pt22Ir23Cu20Au17Ag18 thin films exhibit the formation of two phases. The latter observation is clearly in conflict with the design rules for high entropy alloys. However, the observed phase formation can be rationalized by considering bond strengths and differences in activation energy barriers for surface diffusion. Integrated crystal orbital Hamilton population values per bond imply a decrease in bond strength for all the interactions when Pd is substituted by Ag in PtIrCuAuX which lowers the surface diffusion activation energy barrier by 35% on average for each constituent. This enables the surface diffusion-mediated formation of two phases, one rich in Au and Ag and a second phase enriched in Pt and Cu. Hence, phase formation in these systems appears to be governed by the complex interplay between energetics and kinetic limitations rather than by configurational entropy. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Influence of Ti alloying on thermo-mechanical properties of Mo-Si-B based protective coatings
Authors:E. Aschauer1, V. Dalbauer2, P. Felfer2, V. Moraes3, D. Primetzhofer4, C. Fuger1, O. Hunold5, P. Polcik6, and H. Riedl1,3
Affiliations: 1, Christian Doppler Laboratory for Surface Engineering of high-performance Components, TU Wien, A-1060 Wien, Austria
2, Department of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
3, Institute of Materials Science and Technology, TU Wien, Austria
4, Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala, Sweden
5, Oerlikon Balzers, Oerlikon Surface Solutions AG, Liechtenstein
6, Plansee Composite Materials GmbH, Germany
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