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12 pages, 7564 KiB

Open AccessArticle

Development and Mechanical Characterization of Ni-Cr Alloy Foam Using Ultrasonic-Assisted Electroplating Coating Technique

by Raj Kumar Pittala, Priyaranjan Sharma, Gajanan Anne, Sachinkumar Patil, Vinay Varghese, Sudhansu Ranjan Das, Ch Sateesh Kumar and Filipe Fernandes

Coatings 2023, 13(6), 1002; https://doi.org/10.3390/coatings13061002 - 28 May 2023

Viewed by 1446

Abstract

Metal foams and alloy foams are a novel class of engineering materials and have numerous applications because of their properties such as high energy absorption, light weight and high compressive strength. In the present study, the methodology adopted to develop a Ni-Cr alloy [...] Read more.

Metal foams and alloy foams are a novel class of engineering materials and have numerous applications because of their properties such as high energy absorption, light weight and high compressive strength. In the present study, the methodology adopted to develop a Ni-Cr alloy foam is discussed. Polyurethane (PU) foam of 40PPI (parts per inch) pore density was used as the precursor and coating techniques such as electroless nickel plating (ELN), ultrasonic-assisted electroplating of nickel (UAEPN), and pack cementation or chromizing were used to develop the Ni-Cr alloy foam. The surface morphology, strut thickness and minimum weight gain after each coating stage were evaluated. It was observed from the results that the adopted coating techniques did not damage the original ligament cross-section of the PU precursor. The minimum weight gain and the coating thickness after the UAEPN process were observed to be 42 g and 40–60 μm, respectively. The properties such as porosity percentage, permeability and compressive strength were evaluated. Finally, the pressure drop through the developed foam was estimated and verified to determine whether the developed foam can be used for filtering applications. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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19 pages, 4576 KiB

Open AccessArticle

Comparative Evaluation of Coated Carbide and CBN Inserts Performance in Dry Hard-Turning of AISI 4140 Steel Using Taguchi-Based Grey Relation Analysis

by Mustafa Özdemir, Mohammad Rafighi and Mohammed Al Awadh

Coatings 2023, 13(6), 979; https://doi.org/10.3390/coatings13060979 - 24 May 2023

Cited by 2 | Viewed by 1144

Abstract

Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM [...] Read more.

Dry hard-turning is a vital manufacturing method for machining hardened steel due to its low cost, high machining efficiency, and green environmental protection. This study aims to analyze the effect of various machining parameters on cutting forces and surface roughness by employing RSM and ANOVA. In addition, multi-objective optimization (Grey Relation Analysis: GRA) is performed to determine the optimum machining parameters. Dry hard-turning tests were carried out on AISI 4140 steel (50 HRC) using coated carbide and CBN inserts with different nose radii. The results show that the cutting force components are greatly affected by the cutting depth and cutting speed for both cutting inserts. As the level of cutting depth and cutting speed rise, the cutting forces also increase. However, the feed rate was the main factor in surface roughness. A low feed rate and high cutting speed lead to good surface quality. According to the results, CBN inserts exhibited better performance compared to carbide inserts in terms of minimum cutting forces and surface roughness. The lowest radial force (Fx = 55.59 N), tangential force (Fy = 15.09 N), cutting force (Fz = 30.49 N), and best surface quality (Ra = 0.28 µm, Rz = 1.8 µm) were obtained using a CBN tool. Finally, based on the GRA, the (V = 120 m/min, f = 0.04 mm/rev, a = 0.06 mm, r = 0.8 mm) have been chosen as optimum machining parameters to minimize all responses simultaneously in the machining of AISI 4140 steel using both carbide and CBN inserts. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 5904 KiB

Open AccessArticle

Mechanical Properties and Toughening Mechanisms of Promising Zr-Y-Ta-O Composite Ceramics

by Xiaoteng Fu, Fan Zhang, Wang Zhu and Zhipeng Pi

Coatings 2023, 13(5), 855; https://doi.org/10.3390/coatings13050855 - 30 Apr 2023

Viewed by 1027

Abstract

ZrO₂-YO_1.5-TaO_2.5 (ZYTO) composite ceramics are considered to be a candidate for next-generation thermal barrier coatings (TBCs) due to their excellent thermal stability and low thermal conductivity in high temperatures; however, the mechanical properties and fracture toughness of the [...] Read more.

ZrO₂-YO_1.5-TaO_2.5 (ZYTO) composite ceramics are considered to be a candidate for next-generation thermal barrier coatings (TBCs) due to their excellent thermal stability and low thermal conductivity in high temperatures; however, the mechanical properties and fracture toughness of the ZYTO system may be shortcomings compared with 7-8YSZ: the traditional TBC. In this study, ZYTO composite ceramics were successfully prepared by chemical coprecipitation reaction, and the microstructure of resulting composites was studied as a function of the doping of M-YTaO₄. Mechanical properties, including the density, porosity, hardness and Young’s modulus, were all determinate; the toughening mechanism was verified by the crack growth behavior of the Vickers indentation test. The results suggest that M-YTaO₄ refined the fluorite phase grain and strengthened the grain interface in the composite ceramic. The thermal mismatch between the second phase and matrix produced residual stress in the bulk and affected the crack propagation behavior. With the increase in M-YTaO₄ doping, the grain coarsening and ferroelastic domains were observed in the experiments. The ferroelastic domains with orthogonal polarization directions near the crack tip evidenced the ferroelastic toughening mechanism. The competition among these crack behaviors, such as crack deflection, bridging and bifurcation, dominated the actual fracture toughness of the composite. The best toughening formula was determined in the two-phase region, and the highest indentation fracture toughness was about 42 J/m², which was very close to 7-8YSZ’s 45 ± 5 J/m². Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 8096 KiB

Open AccessArticle

Influence of TiC Addition on Corrosion and Tribocorrosion Resistance of Cr₂Ti-NiAl Electrospark Coatings

by Konstantin A. Kuptsov, Mariya N. Antonyuk, Alexander N. Sheveyko, Andrey V. Bondarev and Dmitry V. Shtansky

Coatings 2023, 13(2), 469; https://doi.org/10.3390/coatings13020469 - 18 Feb 2023

Cited by 1 | Viewed by 1526

Abstract

Marine and coastal infrastructures usually suffer from synergetic effect of corrosion and wear known as tribocorrosion, which imposes strict requirements on the structural materials used. To overcome this problem, novel composite wear- and corrosion-resistant xTiC-Fe-CrTiNiAl coatings with different TiC content were successfully developed. [...] Read more.

Marine and coastal infrastructures usually suffer from synergetic effect of corrosion and wear known as tribocorrosion, which imposes strict requirements on the structural materials used. To overcome this problem, novel composite wear- and corrosion-resistant xTiC-Fe-CrTiNiAl coatings with different TiC content were successfully developed. The coatings were obtained by the original technology of electrospark deposition in a vacuum using xTiC-Cr₂Ti-NiAl (x = 0, 25, 50, 75%) electrodes. The structure and morphology of the coatings were studied in detail by XRD, SEM, and TEM. The effect of TiC content on the tribocorrosion behavior of the coatings was estimated using tribological and electrochemical (under stationary and wear conditions) experiments, as well as impact testing, in artificial seawater. The TiC-free Fe-Cr₂Ti-NiAl coating revealed a defective inhomogeneous structure with transverse and longitudinal cracks. Introduction of TiC allowed us to obtain coatings with a dense structure without visible defects and with uniformly distributed carbide grains. The TiC-containing coatings were characterized by a hardness and elastic modulus of up to 10.3 and 158 GPa, respectively. Formation of a composite structure with a heavily alloyed corrosion-resistant matrix based on α-(Fe,Cr) solid solution and uniformly distributed TiC grains led to a significant increase in resistance to stationary corrosion and tribocorrosion in artificial seawater. The best 75TiC-Fe-CrTiNiAl coating demonstrated the lowest corrosion current density values both under stationary (0.03 μA/cm²) and friction conditions (0.8 μA/cm²), and was characterized by both a 2-2.5 times lower wear rate (4 × 10⁻⁶ mm³/Nm) compared to AISI 420S steel and 25TiC-Fe-CrTiNiAl and a high fracture toughness. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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17 pages, 6938 KiB

Open AccessFeature PaperArticle

CMAS Corrosion Resistance Behavior and Mechanism of Hf₆Ta₂O₁₇ Ceramic as Potential Material for Thermal Barrier Coatings

by Sai Liu, Qing Liu, Xiaopeng Hu, Jinwei Guo, Wang Zhu, Fan Zhang and Jie Xia

Coatings 2023, 13(2), 404; https://doi.org/10.3390/coatings13020404 - 10 Feb 2023

Cited by 6 | Viewed by 1526

Abstract

Thermal barrier coatings (TBCs) have been seriously threatened by calcium-magnesium-alumina-silicate (CMAS) corrosion. The search for novel ceramic coatings for TBCs with excellent resistance to CMAS corrosion is ongoing. Herein, CMAS corrosion resistance behavior and the mechanism of a promising Hf₆Ta₂ [...] Read more.

Thermal barrier coatings (TBCs) have been seriously threatened by calcium-magnesium-alumina-silicate (CMAS) corrosion. The search for novel ceramic coatings for TBCs with excellent resistance to CMAS corrosion is ongoing. Herein, CMAS corrosion resistance behavior and the mechanism of a promising Hf₆Ta₂O₁₇ ceramic coating for TBCs are investigated. The results show that temperature is the most important factor affecting the CMAS behavior and mechanism. At 1250 °C, the corrosion products are composed of dense reaction products (HfSiO₄, Ca_XHf_6−xTa₂O_17−x) and CMAS self-crystallization products. At 1300 and 1400 °C, the corrosion products are mainly dense CaTa₂O₆ and HfO₂, which prevent further CMAS infiltration. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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12 pages, 3564 KiB

Open AccessArticle

The Influence of H Content on the Properties of a-C(W):H Coatings

by Manuel Evaristo, Filipe Fernandes, Chris Jeynes and Albano Cavaleiro

Coatings 2023, 13(1), 92; https://doi.org/10.3390/coatings13010092 - 03 Jan 2023

Cited by 4 | Viewed by 1509

Abstract

Diamond-like-carbon “DLC” coatings can be deposited in many different ways, giving a large range of material properties suitable for many different types of applications. Hydrogen content significantly influences the mechanical properties and the tribological behavior of DLC coatings, but its determination requires techniques [...] Read more.

Diamond-like-carbon “DLC” coatings can be deposited in many different ways, giving a large range of material properties suitable for many different types of applications. Hydrogen content significantly influences the mechanical properties and the tribological behavior of DLC coatings, but its determination requires techniques that are not available in many research centers. Thus, it is important to find alternative indirect techniques, such as Raman spectroscopy or nanoindentation (hardness measurements), which can give comparative and indicative values of the H contents in the coatings, particularly when depositions with a reactive gas flow are being studied. In this work, “DLC” composite coatings with varying H content were deposited via Physical Vapor Deposition (PVD) magnetron sputtering in a reactive atmosphere (Ar + CH₄). An Ion Beam Analysis was used to determine the elemental depth profile across the coating thickness (giving both average C:W:H ratios and film density when combined with profilometer measurements of film thickness). The hardness was evaluated with nanoindentation, and a decrease from 16 to 6 GPa (and a decrease in the film density by a factor of two) with an increasing CH₄ flow was observed. Then, the hardness and Raman results were correlated with the H content in the coatings, showing that these indirect methods can be used to find if there are variations in the H content with the increase in the CH₄ flow. Finally, the adhesion and tribological performance of the coatings were evaluated. No significant differences were found in the adhesion as a function of the H content. The tribological properties presented a slight improving trend with the increase in the H content with a decrease in the wear rate and friction. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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14 pages, 2477 KiB

Open AccessArticle

Effect of Standoff Distance on Corrosion Resistance of Cold Sprayed Titanium Coatings

by Mieczyslaw Scendo and Katarzyna Staszewska-Samson

Coatings 2022, 12(12), 1853; https://doi.org/10.3390/coatings12121853 - 30 Nov 2022

Viewed by 1363

Abstract

A titanium protective layer was deposited onto Al7075 substrate (Al7075/Ti) by a cold spray method (CS) with different standoff distances (SoD) of the nozzle from the specimen surface. The aim of this research was to study the influence on the mechanical properties and [...] Read more.

A titanium protective layer was deposited onto Al7075 substrate (Al7075/Ti) by a cold spray method (CS) with different standoff distances (SoD) of the nozzle from the specimen surface. The aim of this research was to study the influence on the mechanical properties and corrosion resistance of the Ti coating on Al7075 substrate. The surface and microstructure of Al7075/Ti was observed by a scanning electron microscope (SEM). The corrosion test of the materials was carried out by using the electrochemical method. The SoD had a significant effect on the microstructure of the coatings and their adhesion onto Al7075 substrate. The highest level of microhardness (248 HV0.3) value was achieved for deposits obtained with the SoD of 70 mm. The corrosion tests showed that the mechanism of electrochemical corrosion of titanium coatings is a multi-stage process, and the main product of the corrosion process was (TiO₂)_ads. However, the polarization resistance (Rp = 49 kΩ cm²) of the Al7075/Ti coatings was the highest, while the corrosion rate (υ_corr = 13.90 mm y⁻¹) was the lowest, for SoD of 70 mm. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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18 pages, 6047 KiB

Open AccessArticle

Quantitative Characterization of Interfacial Defects in Thermal Barrier Coatings by Long Pulse Thermography

by Jinfeng Wei, Guangnan Xu, Guolin Liu, Jinwei Guo, Wang Zhu and Zengsheng Ma

Coatings 2022, 12(12), 1829; https://doi.org/10.3390/coatings12121829 - 26 Nov 2022

Cited by 2 | Viewed by 1037

Abstract

The non-contact long pulse thermography method is commonly used to detect the defects in thermal barrier coatings (TBCs). The profile of interfacial defect in TBCs can be monitored by infrared camera under the irradiation of the excitation source. Unfortunately, the defect profile is [...] Read more.

The non-contact long pulse thermography method is commonly used to detect the defects in thermal barrier coatings (TBCs). The profile of interfacial defect in TBCs can be monitored by infrared camera under the irradiation of the excitation source. Unfortunately, the defect profile is always blurry due to heat diffusion between the defect area and the intact area. It is difficult to quantify the size of defect size in TBCs. In this work, combined with derived one-dimensional heat conduction analytical model, a non-contact long pulse thermography (LPT) method is applied to quantitatively investigate the interface defects in TBCs. Principal component analysis (PCA) and background subtraction method are used to improve the contrast of the defect profile in collected thermal images. By fitting the results between the profile of the interface defect in thermal images and the predicted shape of the model, the interface defect size can be determined. Furthermore, a simple extension of proposed method for interfacial defects with irregular shape is presented. The predicted errors for round defect with diameters of 3 mm, 5 mm and 7 mm are roughly distributed in the range of 3%~6%, which are not affected by the defect diameter. Full article

(This article belongs to the Special Issue Advanced Nano-Structured Hard Coatings: Design, Synthesis, and Applications)

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