Materials

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15 pages, 8017 KiB

Open AccessArticle

Deposition of NiAl/Al₃Ni₂(CrB₂) Coatings from Ni, Al and CrB₂ Powders Using Mechanical Synthesis in Planetary Ball Mill

by Maciej Szlezynger, Daniel Toboła and Jerzy Morgiel

Materials 2024, 17(2), 492; https://doi.org/10.3390/ma17020492 - 19 Jan 2024

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Interest in composite thick coatings with an intermetallic matrix stimulates the development of new deposition techniques like the co-milling of pre-alloyed NiAl powder with platelet-shaped substrates. Obtained coatings were up to several micrometers thick as cold-welding of intermetallic particles was effective only at [...] Read more.

Interest in composite thick coatings with an intermetallic matrix stimulates the development of new deposition techniques like the co-milling of pre-alloyed NiAl powder with platelet-shaped substrates. Obtained coatings were up to several micrometers thick as cold-welding of intermetallic particles was effective only at the start of this process, while later, chipping prevailed over added material. The present experiment covered the co-milling in the planetary ball mill of Ni and Al elemental powders (1:1 molar ratio) with AISI 304 steel platelets for 32 h at 300 rpm. Next, this process was repeated with an admixture of 15 wt.% of CrB₂ powder. In both cases, their milling succeeded in producing up to a 200 μm coating after 4 h. The use of light, scanning and transmission electron microscopy (LM/SEM/TEM) helped to establish that the coatings had gradient microstructures with more refined crystallites of NiAl, Al₃Ni₂ and CrB₂ closer to the surface. With the addition of a ceramic phase, the coatings presented higher hardness and lower friction during dry wear tests both at RT and at 500 °C. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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16 pages, 8552 KiB

Open AccessArticle

A Comprehensive Investigation of the Mechanical and Tribological Properties of AZO Transparent Conducting Oxide Thin Films Deposited by Medium Frequency Magnetron Sputtering

by Michał Mazur, Milena Kiliszkiewicz, Witold Posadowski, Jarosław Domaradzki, Aleksandra Małachowska and Paweł Sokołowski

Materials 2024, 17(1), 81; https://doi.org/10.3390/ma17010081 - 23 Dec 2023

Viewed by 782

Abstract

This paper presents a detailed analysis of aluminium-doped zinc oxide (AZO) thin films and considers them a promising alternative to indium tin oxide in transparent electrodes. The study focusses on critical properties of AZO, including optical, electrical, and mechanical properties, with potential applications [...] Read more.

This paper presents a detailed analysis of aluminium-doped zinc oxide (AZO) thin films and considers them a promising alternative to indium tin oxide in transparent electrodes. The study focusses on critical properties of AZO, including optical, electrical, and mechanical properties, with potential applications in displays, photovoltaic cells, and protective coatings. The deposited AZO thin films are characterised by excellent optical and electrical parameters, with transparency in the visible light range exceeding 80% and resistivity of 10⁻³ Ω·cm, which gives a high value of figure of merit of 63. Structural analysis confirms the nanocrystalline nature of as-deposited AZO thin films, featuring hexagonal ZnO, orthorhombic Al₂O₃, and cubic Al₂ZnO₄ phases. The study includes nanoindentation measurements, which reveal exceptional hardness (11.4 GPa) and reduced elastic modulus (98 GPa), exceeding typical values reported in the literature, highlighting their protective potential. Abrasion tests have shown extraordinary scratch resistance due to the lack of impact on topography and surface roughness up to 10,000 cycles. This comprehensive study demonstrated that as-deposited AZO thin films are multifunctional materials with exceptional optical, electrical, and mechanical properties. The findings open up possibilities for a variety of applications, especially in protective coatings, where the combination of hardness, scratch resistance, and transparency is both rare and valuable. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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16 pages, 18225 KiB

Open AccessArticle

Novel Cr/Si-Slurry Diffusion Coatings for High Temperatures

by Michael Kerbstadt, Emma Marie Hamilton White and Mathias Christian Galetz

Materials 2023, 16(23), 7480; https://doi.org/10.3390/ma16237480 - 02 Dec 2023

Cited by 1 | Viewed by 1227

Abstract

Surface enrichment in Al, Si, and Cr can greatly improve high temperature oxidation resistance of many alloys. Al, Si, and Cr coatings are commonly applied via simple slurries or more complex pack cementation processes. Due to the high melting point of Cr, the [...] Read more.

Surface enrichment in Al, Si, and Cr can greatly improve high temperature oxidation resistance of many alloys. Al, Si, and Cr coatings are commonly applied via simple slurries or more complex pack cementation processes. Due to the high melting point of Cr, the deposition of Cr-based diffusion coatings by the slurry technique has proved challenging, and to date, Cr has mostly been applied by pack cementation. Here, a novel Cr-Si coating process via the slurry technique is described which has been developed and then demonstrated on two Ni-based superalloys, Rene 80 and Inconel 740H. The addition of Si to the slurry lowers the melting point via a Cr-Si eutectic and enables the formation of a liquid phase during heat treatment. Through this Cr-Si slurry coating process diffusion layers enriched by Cr and Si of about 150 µm were achieved. Oxidation behavior was studied through isothermal exposures at 900 °C for 1000 h in lab air. Uncoated Rene 80 and IN740H both showed formation of a Ti-containing Cr₂O₃ scale below a thin TiO₂ top layer. Underneath the external scale a zone of internally oxidized Al grew over the exposure time and reduced the load-bearing cross-section progressively. In comparison, the Cr/Si-coated samples did not show internal Al oxidation, but a slow-growing Si-rich oxide film underneath the external Cr₂O₃ scale. This subscale represents an additional oxygen diffusion barrier. Thus, the weight gain during exposure for the coated samples was significantly lower than for the uncoated materials. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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11 pages, 5606 KiB

Open AccessArticle

Zirconium Surface Treatment via Chemical Etching

by Przemysław Gołasz, Agata Kołkowska, Rafał Zieliński and Wojciech Simka

Materials 2023, 16(23), 7404; https://doi.org/10.3390/ma16237404 - 28 Nov 2023

Cited by 1 | Viewed by 792

Abstract

The increased demand for implants that do not pose a threat to patients diagnosed using high-resolution magnetic resonance imaging and concerns arising from titanium allergies require the development of alternative implant materials. One promising concept is a use of zirconium as corrosion-resistant, nontoxic [...] Read more.

The increased demand for implants that do not pose a threat to patients diagnosed using high-resolution magnetic resonance imaging and concerns arising from titanium allergies require the development of alternative implant materials. One promising concept is a use of zirconium as corrosion-resistant, nontoxic material that is lower in magnetic susceptibility. To achieve this, safe and efficient surface treatment methods of zirconium metal have to be developed. In this study, zirconium samples were treated with fluoride-free and fluoride-containing etching mixtures to determine their effect on the surface of Zr. SEM images were taken to investigate the preliminary effects of the etchants. Then, a second set of experiments was carried out using mixtures of HF-H₂SO₄ and ammonium persulfate–fluoride salts, as they gave the most promising results in the first trial. SEM images were taken and measurements on roughness, wettability, and atomic composition were made. The results showed an even zirconium surface in APS-fluoride salts, along with the formation of pits (1–3 μm) similar to those found in commercially available implants. There was no significant increase in the roughness of the treated samples. The addition of NO₃⁻ ions in the form of KNO₃ speeded up etching and promoted pit formation. The HF-H₂SO₄ mixture was found to give unsatisfying results, as the surface was too rough and the formed pits were too large. It was concluded that etching zirconium in ammonium persulfate and fluoride salts is a promising area of research for the preparation of zirconium implants; however, further research has to be carried out on sandblasted samples. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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15 pages, 10795 KiB

Open AccessArticle

Microstructure and Corrosion Behavior of ZnAl12Mg3Si0.3 Double-Batch Hot-Dip Coatings

by Henryk Kania, Anżelina Marek, Michał Zoran, Marcin Spławski, Przemysław Kupczyk, Mateusz Wiewióra and Aleksandra Kupczyk

Materials 2023, 16(6), 2162; https://doi.org/10.3390/ma16062162 - 08 Mar 2023

Cited by 1 | Viewed by 1406

Abstract

This article presents the microstructure (SEM) and corrosion behavior of ZnAl12Mg3Si0.3 (ZAMS) coatings obtained by the double hot-dip method on Sebisty steel with increased strength. On the basis of chemical composition studies in micro-areas (EDS) and phase composition studies (XRD), structural components of [...] Read more.

This article presents the microstructure (SEM) and corrosion behavior of ZnAl12Mg3Si0.3 (ZAMS) coatings obtained by the double hot-dip method on Sebisty steel with increased strength. On the basis of chemical composition studies in micro-areas (EDS) and phase composition studies (XRD), structural components of the coating and corrosion products formed on the coating surface after exposure to the neutral salt spray (NSS) test (EN ISO 9227) were identified. The presence of the Fe(Al,Si,Zn)₃ intermetallic phase was found in the Fe-Al intermetallic layer, while in the outer layer, dendrites rich in Al and Zn were identified. In these dendrites, the eutectics of Zn/MgZn₂ and precipitates of the MgZn₂ phase and Si were located. The NSS test showed better corrosion resistance of ZAMS coatings compared to conventional zinc hot-dip coatings. The increase in corrosion resistance is due to the formation of favorable corrosion products: simonkolleite—Zn₅(OH)₈Cl₂·H₂O and hydrozincite—Zn₅(OH)₆(CO₃)₂, and the presence of the MgZn₂ phase in the coating, which is more anodic than other structural components. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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14 pages, 5530 KiB

Open AccessFeature PaperArticle

Hot Corrosion Behavior of TWAS and HVOF NiCr-Based Coatings in Molten Salt

by Kateřina Lencová, Marie Frank Netrvalová, Marek Vostřák, František Lukáč, Radek Mušálek, Zdeněk Česánek and Šárka Houdková

Materials 2023, 16(4), 1712; https://doi.org/10.3390/ma16041712 - 18 Feb 2023

Cited by 3 | Viewed by 1425

Abstract

In order to extend the life of boilers by applying an anti-corrosion coating without the need to dismantle them, it is advisable to find coatings that can be applied using cheaper and portable techniques, such as Twin Wire Arc Spray technology (TWAS). In [...] Read more.

In order to extend the life of boilers by applying an anti-corrosion coating without the need to dismantle them, it is advisable to find coatings that can be applied using cheaper and portable techniques, such as Twin Wire Arc Spray technology (TWAS). In this study, we compare selected NiCr-based coatings and two uncoated steel substrates (steel 1.7715 and 1.4903). Two coatings, Cr₃C₂ - 25% NiCr and Hastelloy C-276 are deposited using High velocity oxygen-fuel technology (HVOF) and three coatings, NiCrTi, NiCrMo, and Inconel 625, are deposited using TWAS. In addition to the corrosion weight gain during 50 cycles of loading in an 18% Na₂SO₄ and 82% Fe₂(SO₄)₃ salt environment at 690 °C evaluated using the gravimetric method, the microstructure and phase composition of the coatings were analyzed on the samples after the exposure in order to compare the properties and gain a deeper understanding of the corrosion kinetics. Coating cross-sections and free-surfaces were observed with a scanning electron microscope (SEM) with an energy-dispersive (EDX) system. The phase composition was investigated using X-ray diffraction (XRD) and Raman spectroscopy. No significant differences were observed between the TWAS and HVOF coating methods for the coatings compared. Due to the similar corrosion products found on all coatings, a very effective corrosion protective layer was formed on the surface, forming a barrier between the corrosive environment and the coating regardless of the used deposition technology. Therefore, for industrial use on the inner surface of coal-fired boilers we recommend NiCrTi, NiCrMo, or Inconel coatings prepared with the more cost-effective and portable TWAS technology. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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13 pages, 5426 KiB

Open AccessArticle

Electrochemical Behavior of SiC-Coated AA2014 Alloy through Plasma Electrolytic Oxidation

by Talal A. Aljohani, Majed O. Alawad, Sally Elkatatny, Abdulrahman I. Alateyah, Meteb T. Bin Rubayan, Mohammed A. Alhajji, Muntathir I. AlBeladi, Fuad Khoshnaw and Waleed H. El-Garaihy

Materials 2022, 15(10), 3724; https://doi.org/10.3390/ma15103724 - 23 May 2022

Cited by 4 | Viewed by 1988

Abstract

In this study, the corrosion performance of AA2014 aluminum alloy was enhanced by coating the alloy with a layer containing silica (SiC) that was formed by the plasma electrolytic oxidation (PEO) process. The PEO process was performed with different electrical parameters (frequency, current [...] Read more.

In this study, the corrosion performance of AA2014 aluminum alloy was enhanced by coating the alloy with a layer containing silica (SiC) that was formed by the plasma electrolytic oxidation (PEO) process. The PEO process was performed with different electrical parameters (frequency, current mode, and duty ratio) and both with and without SiC to investigate the microstructural and electrochemical differences in the coated samples produced from the process. The microstructure and composition of the PEO coatings were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). A potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the AA2014-PEO-coated samples. The potentiodynamic polarization showed that the SiC-PEO-coated samples had a significantly decreased corrosion rate (99.8%) compared with the uncoated AA2014 Al alloy. Our results showed that the coats containing SiC possessed a much higher corrosion resistance than both the uncoated AA2014 Al alloy (8,344,673%) and the SiC-free coatings, which possess low corrosion resistance, because of their higher chemical stability and more compact microstructure. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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14 pages, 5465 KiB

Open AccessEditor’s ChoiceArticle

Effects of Stepped Heating on the Initial Growth of Oxide Scales on NiCrAlHf Bond Coat Alloy under Air and Water Vapor Atmospheres

by Yang He, Biju Zheng, Peng Song, Taihong Huang, Hezhong Pei, Bixiao Yang and Shakeel Shakeel

Materials 2022, 15(8), 2914; https://doi.org/10.3390/ma15082914 - 15 Apr 2022

Cited by 1 | Viewed by 1465

Abstract

Temperature and atmosphere have a significant effect on the oxidation of MCrAlY (M = Ni, Co) bond coating. The initial growth behavior of the NiCrAlHf bond coat alloy was investigated at 1100 °C under different atmospheric conditions and using heating methods. A thick [...] Read more.

Temperature and atmosphere have a significant effect on the oxidation of MCrAlY (M = Ni, Co) bond coating. The initial growth behavior of the NiCrAlHf bond coat alloy was investigated at 1100 °C under different atmospheric conditions and using heating methods. A thick Al₂O₃ oxide layer and large HfO₂ particles were observed, perhaps due to metastable oxide growth at low temperatures when using stepped heating. However, in air and water vapor atmospheres, the oxide scale was thinner and the HfO₂ precipitates were smaller in stepped heating than in constant heating. The size and distribution of the HfO₂ particles might have induced different microstructures, particularly voids within the oxide scale. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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16 pages, 5870 KiB

Open AccessArticle

Formation of Composite Coatings on Galvanized Steel from Organosilane Solutions Using Electrophoresis and Sol–Gel Technology

by Yuriy B. Makarychev, Natalia A. Gladkikh, Galina V. Redkina, Oleg Yu. Grafov, Ali D. Aliev and Yuriy I. Kuznetsov

Materials 2022, 15(7), 2418; https://doi.org/10.3390/ma15072418 - 25 Mar 2022

Cited by 3 | Viewed by 1730

Abstract

New hybrid composite coatings (HCCs) on hot-dip galvanized steel (HDGS) were obtained using electrophoresis (cathodic polarization (CP)) and sol–gel technology. For this purpose, a technique for the preparation of a cationic precursor based on TiCl₄ and aminopropyltriethoxysilane was developed. Electrophoresis of the [...] Read more.

New hybrid composite coatings (HCCs) on hot-dip galvanized steel (HDGS) were obtained using electrophoresis (cathodic polarization (CP)) and sol–gel technology. For this purpose, a technique for the preparation of a cationic precursor based on TiCl₄ and aminopropyltriethoxysilane was developed. Electrophoresis of the charged particles of the precursor and organosilanes promotes the production of denser sol–gel coatings with improved adhesion. Using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) methods, the formation mechanism and protective properties of HCC on galvanized steel were investigated. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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17 pages, 4547 KiB

Open AccessArticle

Corrosion Resistance Mechanism of Mica–Graphene/Epoxy Composite Coating in CO₂-Cl⁻ System

by Shi-Dong Zhu, Yan-Peng Li, Hong-Wei Wang, Jin-Ling Li, An-Qing Fu, Gang Chen, Dong Ma, Xuan-Peng Li and Frank Cheng

Materials 2022, 15(3), 1194; https://doi.org/10.3390/ma15031194 - 04 Feb 2022

Cited by 2 | Viewed by 1691

Abstract

The working environment for tubing in oil and gas fields is becoming more and more serious due to the exploration of unconventional oil and gas resources, leading to the increasing need for a protective internal coating to be used in tubing. Therefore, a [...] Read more.

The working environment for tubing in oil and gas fields is becoming more and more serious due to the exploration of unconventional oil and gas resources, leading to the increasing need for a protective internal coating to be used in tubing. Therefore, a new mica–graphene/epoxy composite coating with different graphene contents (0.0, 0.2, 0.5, 0.7, and 1.0 wt.%) was prepared to improve the tubing resistance to a corrosive medium, an autoclave was used to simulate the working environment, and an electrochemical workstation assisted by three-electrodes was used to study the electrochemical characteristics of the coating. The results showed that the addition of a certain amount of graphene into the mica/epoxy coating significantly improved the corrosion resistance of the composite coating, and when the graphene content increased, the corrosion resistance of the mica/epoxy coating first increased and then decreased when the corrosion current density of a 35 wt.% 800^# mica/epoxy coating with a 0.7 wt.% graphene content was the lowest (7.11 × 10⁻¹³ A·cm⁻²), the corrosion potential was the highest (292 mV), the polarization resistance was the largest (3.463 × 10⁹ Ω·cm²), and the corrosion resistance was improved by 89.3% compared to the coating without graphene. Furthermore, the adhesion of the coating with 0.7 wt.% graphene was also the largest (8.81 MPa, increased by 3.4%) and had the smallest diffusion coefficient (1.566 × 10⁷ cm²·s⁻¹, decreased by 76.1%), and the thermal stability improved by 18.6%. Finally, the corrosion resistance mechanism of the composite coating with different graphene contents at different soaking times was revealed based on the electrochemistry and morphology characteristics other than water absorption and contact angle. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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14 pages, 9965 KiB

Open AccessArticle

Influence of Test Conditions on Sliding Wear Performance of High Velocity Air Fuel-Sprayed WC–CoCr Coatings

by Kaveh Torkashvand, Vinod Krishna Selpol, Mohit Gupta and Shrikant Joshi

Materials 2021, 14(11), 3074; https://doi.org/10.3390/ma14113074 - 04 Jun 2021

Cited by 8 | Viewed by 1659

Abstract

Sliding wear performance of thermal spray WC-based coatings has been widely studied. However, there is no systematic investigation on the influence of test conditions on wear behaviour of these coatings. In order to have a good understanding of the effect of test parameters [...] Read more.

Sliding wear performance of thermal spray WC-based coatings has been widely studied. However, there is no systematic investigation on the influence of test conditions on wear behaviour of these coatings. In order to have a good understanding of the effect of test parameters on sliding wear test performance of HVAF-sprayed WC–CoCr coatings, ball-on-disc tests were conducted under varying test conditions, including different angular velocities, loads and sliding distances. Under normal load of 20 N and sliding distance of 5 km (used as ‘reference’ conditions), it was shown that, despite changes in angular velocity (from 1333 rpm up to 2400 rpm), specific wear rate values experienced no major variation. No major change was observed in specific wear rate values even upon increasing the load from 20 N to 40 N and sliding distance from 5 km to 10 km, and no significant change was noted in the prevailing wear mechanism, either. Results suggest that no dramatic changes in applicable wear regime occur over the window of test parameters investigated. Consequently, the findings of this study inspire confidence in utilizing test conditions within the above range to rank different WC-based coatings. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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14 pages, 4333 KiB

Open AccessArticle

Comparison of the Tribological Properties of the Thermal Diffusion Zinc Coating to the Classic and Heat Treated Hot-Dip Zinc Coatings

by Dariusz Jędrzejczyk and Wojciech Skotnicki

Materials 2021, 14(7), 1655; https://doi.org/10.3390/ma14071655 - 28 Mar 2021

Cited by 5 | Viewed by 2357

Abstract

The presented studies are focused on the wear resistance and friction coefficient changes of the thermal diffusion (TD) zinc coating deposited on steel. The aim of research was to evaluate the variation in coating properties during dry friction as a result of the [...] Read more.

The presented studies are focused on the wear resistance and friction coefficient changes of the thermal diffusion (TD) zinc coating deposited on steel. The aim of research was to evaluate the variation in coating properties during dry friction as a result of the method of preparation of the basis metal. The measured properties were compared to those obtained after classic hot-dip (HD) zinc galvanizing—heat treated and untreated. Thermal diffusion zinc coatings were deposited in industrial conditions (according to EN ISO 17668:2016-04) on disc-shaped samples. The results obtained during the tribological tests (T11 pin-on-disc tester) were analysed on the basis of microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis and microhardness measurements. The obtained results were similar to effects observed after heat treatment of HD zinc coating. The conducted analysis proved that the method of initial steel surface preparation results in changes in the coating’s hardness, friction coefficient and wear resistance. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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12 pages, 10828 KiB

Open AccessArticle

Active IR Thermography Evaluation of Coating Thickness by Determining Apparent Thermal Effusivity

by Alexey Moskovchenko, Vladimir Vavilov, Michal Švantner, Lukáš Muzika and Šárka Houdková

Materials 2020, 13(18), 4057; https://doi.org/10.3390/ma13184057 - 12 Sep 2020

Cited by 17 | Viewed by 2505

Abstract

Pulsed thermography is a common technique for nondestructive testing (NDT) of materials. This study presents the apparent effusivity method for the quantitative evaluation of coating thickness in a one-sided thermal NDT procedure. The proposed algorithm is based on determining a threshold value of [...] Read more.

Pulsed thermography is a common technique for nondestructive testing (NDT) of materials. This study presents the apparent effusivity method for the quantitative evaluation of coating thickness in a one-sided thermal NDT procedure. The proposed algorithm is based on determining a threshold value of apparent effusivity, which can be found for particular coating-on-substrate structures. It has been found that the square root of the time at which the apparent effusivity curve reaches this threshold is proportional to the coating thickness. The efficiency of the proposed approach is demonstrated by analytical modeling and experimentation performed on thermally-sprayed coatings. Full article

(This article belongs to the Special Issue Microstructure, Tribological and Corrosion Behaviors of Coatings)

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