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14 pages, 6972 KiB

Open AccessArticle

Microstructural and Mechanical Properties Analysis of Phosphate Layers Deposited on Steel Rebars for Civil Constructions

by Petru Lazar, Nicanor Cimpoesu, Bogdan Istrate, Alin Marian Cazac, Diana-Petronela Burduhos-Nergis, Marcelin Benchea, Andrei-Constantin Berbecaru, Gheorghe Badarau, Gabriel Dragos Vasilescu, Mihai Popa and Costica Bejinariu

Coatings 2024, 14(2), 182; https://doi.org/10.3390/coatings14020182 - 31 Jan 2024

Cited by 1 | Viewed by 864

Abstract

This paper carries out a study on the microstructural characteristics and mechanical properties of phosphate layers deposited on steel reinforcements for civil constructions. Analyses were performed on 4 sets of samples: 1 control sample (unphosphated) and 2–4 samples that were phosphated with three [...] Read more.

This paper carries out a study on the microstructural characteristics and mechanical properties of phosphate layers deposited on steel reinforcements for civil constructions. Analyses were performed on 4 sets of samples: 1 control sample (unphosphated) and 2–4 samples that were phosphated with three different solutions. The structural and chemical analysis, as well as the examination of the mechanical properties (surface roughness, microindentation, and scratch resistance) of the phosphate layers deposited on steel rebars for civil constructions, was carried out. The following conclusions were drawn from the experimental results: the coatings show flashes of crystals deposited on the metal surface; chemical homogenization of the phosphated layers is observed; the profiles present a higher roughness after deposition of the phosphated layers; the indentation Young modulus and hardness values recommend the phosphating procedure to improve the CS surface quality; the COF is three times larger for phosphated samples compared with the initial metallic one; and scratch traces are uninterrupted, except for one zone of sample that was phosphated with solution II, wherein the phosphated layer does not present lateral scratches or exfoliations. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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10 pages, 8083 KiB

Open AccessArticle

Enhancement of Spreadability in Haynes 230 Powder via In Situ Micro-Oxidation Gas Atomization for Additive Manufacturing Process

by Peng Zhang, Zhongnan Bi, Rui Wang, Lianbo Wang, Guohao Liu, Guangbao Sun and Shaoming Zhang

Coatings 2024, 14(2), 177; https://doi.org/10.3390/coatings14020177 - 31 Jan 2024

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Abstract

The powder bed packing density of metal powders plays a crucial role in additive manufacturing as it directly affects the defect and mechanical properties of the fabricated parts. Powder bed packing density is related to powder flowability and spreadability. In this study, we [...] Read more.

The powder bed packing density of metal powders plays a crucial role in additive manufacturing as it directly affects the defect and mechanical properties of the fabricated parts. Powder bed packing density is related to powder flowability and spreadability. In this study, we introduced a new method to improve powder flowability and spreadability, where Haynes 230 powder with exceptional flowability was successfully produced using an in situ micro-oxidation gas atomization process. Compared to conventional gas atomization, the powder exhibited improved flowability and spreadability, measuring at 11.8 s/50 g. Additionally, the angle of repose was reduced by 25%, resulting in a powder bed packing density of 5.67 g/cm³, corresponding to 63.7% of the theoretical density. Notably, the oxygen content in the powder was only 180 ppm, as confirmed by XRD testing, and no oxide peaks were detected. Furthermore, the depth of the oxide layer on the particle surface increased by less than 20 nm. As a result, the in situ micro-oxidation process reduces the number of pores and cracks in the Haynes 230 alloy formed specimens and improves the relative density of the built specimens. This study highlights the potential of in situ micro-oxidation gas atomization as a promising method for producing powders with high flowability and spreadability for laser powder bed fusion (LPBF) processes. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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20 pages, 11184 KiB

Open AccessArticle

The Effect of a Coating on the Crystallization of Multicomponent Co-Based Amorphous Alloys

by Galina Abrosimova, Valentina Chirkova, Nikita Volkov, Boris Straumal and Alexandr Aronin

Coatings 2024, 14(1), 116; https://doi.org/10.3390/coatings14010116 - 15 Jan 2024

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Abstract

The effect of protective coatings on the crystallization of amorphous Co-based alloys was studied using the methods of X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The crystallization of the amorphous alloys was studied on as-prepared samples, deformed samples, and deformed samples [...] Read more.

The effect of protective coatings on the crystallization of amorphous Co-based alloys was studied using the methods of X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The crystallization of the amorphous alloys was studied on as-prepared samples, deformed samples, and deformed samples with a protective coating. After heat treatment, the fraction of the crystalline phase in the pre-deformed samples was higher than in the undeformed samples. When using a protective coating, the fraction of nanocrystals formed during heat treatment increased. The size of the crystals formed in deformed samples was smaller, and in the deformed samples with a protective coating, they were slightly larger than in the corresponding initial samples. The reasons for the differences in the formed structure in the amorphous alloys under study are discussed in terms of free volume. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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9 pages, 5072 KiB

Open AccessArticle

Rolling Contact Fatigue Damage Analysis of G10CrNi3Mo Steel Bearing Inner Ring by X-ray Measurements

by Haixia Qu, Lisong Yao and Ke Zhan

Coatings 2023, 13(12), 2021; https://doi.org/10.3390/coatings13122021 - 29 Nov 2023

Viewed by 1010

Abstract

Contact fatigue is the main failure model for bearing systems in steel rolling mills. Characterizing the degree of contact fatigue damage is important for predicting its operating life. In this paper, the X-ray diffraction method (XRD) is used to measure the residual stress [...] Read more.

Contact fatigue is the main failure model for bearing systems in steel rolling mills. Characterizing the degree of contact fatigue damage is important for predicting its operating life. In this paper, the X-ray diffraction method (XRD) is used to measure the residual stress state and the diffraction peak width (FWHM, full width at half maximum) of six samples with different degrees of contact fatigue failure. The results show that surface residual stress values increased by more than 70% compared with the original state, while the diffraction peak width values decreased by more than 7% and were strongly correlated with the degree of contact fatigue damage. The XRD measurement of the bearing inner ring enables the characterization of the evolution of the residual stress state and grain distortion due to damage development. FWHM values may be considered an indicator for predicting the degree of contact fatigue. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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22 pages, 4735 KiB

Open AccessFeature PaperArticle

Induced Codeposition of Tungsten with Zinc from Aqueous Citrate Electrolytes

by Honorata Kazimierczak and Noam Eliaz

Coatings 2023, 13(12), 2001; https://doi.org/10.3390/coatings13122001 - 25 Nov 2023

Viewed by 963

Abstract

Zinc–tungsten coatings have been considered as environmentally friendly, and corrosion- and wear-resistant coatings. Here, Zn–W coatings were successfully electrodeposited from an aqueous solution. Citrate-based electrolytes with pH in the range of 3.0 to 5.7 were used as plating baths. The kinetics of co-reduction [...] Read more.

Zinc–tungsten coatings have been considered as environmentally friendly, and corrosion- and wear-resistant coatings. Here, Zn–W coatings were successfully electrodeposited from an aqueous solution. Citrate-based electrolytes with pH in the range of 3.0 to 5.7 were used as plating baths. The kinetics of co-reduction in the Zn(II)–W(VI)–Cit system was studied on the basis of partial polarization curves. The effects of applied potential, electrolyte composition, pH, hydrodynamic conditions and passed charge on the electrodeposition of Zn–W layers were determined. X-ray photoelectron spectroscopy confirmed the presence of metallic tungsten co-deposited with zinc. X-ray diffraction analysis revealed the formation of hexagonal Zn–W phase resulting from a substitution of Zn atoms by W atoms in the Zn crystal lattice. The formation of the proper stable and electroactive W(VI) and Zn(II) complexes is the first crucial factor enabling the induced codeposition of Zn–W alloys. The tungsten content in the Zn–W deposit is closely related to the concentration of electroactive tungstate–citrate species and its ratio relative to the zinc–citrate electroactive species in the electrolytic bath. The oxidation state of tungsten in the electrodeposited Zn–W layers can be controlled mainly by the applied deposition potential and by the bath pH, which determines the type of W(VI)–Cit species that can be reduced. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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11 pages, 5561 KiB

Open AccessArticle

Effect of Mg Addition on Microstructure and Sacrificial Anode Protection Performance of Hot Dip Al-5Zn-4Si-xMg Coating

by Zhaobin Liu, Jiaxin Li, Haoping Peng, Aijun Xie and Zhiwei Li

Coatings 2023, 13(6), 1087; https://doi.org/10.3390/coatings13061087 - 12 Jun 2023

Cited by 1 | Viewed by 1193

Abstract

The effect of Mg addition on the microstructure and sacrificial anode protection performance of a hot-dip Al-5Zn-4Si-xMg coating was studied by scanning electron microscopy (SEM-EDS), an X-ray diffractometer, and an electrochemical workstation. The results showed that Al-Zn-Si alloy was composed of an Al-rich [...] Read more.

The effect of Mg addition on the microstructure and sacrificial anode protection performance of a hot-dip Al-5Zn-4Si-xMg coating was studied by scanning electron microscopy (SEM-EDS), an X-ray diffractometer, and an electrochemical workstation. The results showed that Al-Zn-Si alloy was composed of an Al-rich phase and a Zn-rich phase. The MgZn₂ phase appears after Mg addition. When the addition of Mg increased to 0.15 wt.%, the Mg₂Si phase began to appear in the alloy. The hot-dip Al-5Zn-4Si-xMg coating consisted of Si particles, an Al-rich phase and a Zn-rich phase. When the Mg content increased to 0.15 wt.%, the Mg₂Si phase and Al + Zn + MgZn₂ eutectoid phase began to appear in the coating. In the full immersion corrosion test of the hot-dip Al-5Zn-4Si-xMg coating, the order of corrosion resistance was 0.15% Mg coating > 0.2% Mg coating > 0.05% Mg coating > 0 Mg coating. In the corrosion process of the hot-dip Al-5Zn-4Si-0.15Mg coating, with the increase in immersion, the self-corrosion current of the coating decreased, and the sacrificial protection performance was the best. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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19 pages, 4843 KiB

Open AccessArticle

Experimental Investigation and Optimization of AZ31 Mg alloy during Warm Incremental Sheet Forming to Study Fracture and Forming Behaviour

by Rohit Magdum and Pandivelan Chinnaiyan

Coatings 2023, 13(1), 68; https://doi.org/10.3390/coatings13010068 - 30 Dec 2022

Cited by 1 | Viewed by 1763

Abstract

The main purpose of this research work is to study the forming limit and fracture behaviour of the AZ31 magnesium alloy, as well as to improve the formability and surface roughness of parts formed using the warm incremental sheet forming (ISF) process. For [...] Read more.

The main purpose of this research work is to study the forming limit and fracture behaviour of the AZ31 magnesium alloy, as well as to improve the formability and surface roughness of parts formed using the warm incremental sheet forming (ISF) process. For the ISF process, AZ31 Mg alloy sheets were used. Initially, Taguchi orthogonal L27 arrays were used to design experiments, and a framed multi-objective optimization problem was solved using the grey-fuzzy method. The strain-based forming fracture limit diagrams (FFLD) were plotted after a variable wall angle test. The grey-fuzzy reasoning grade (GFRG) is calculated in this study by combining grey relational analysis (GRA) and fuzzy rationale. For the AZ31 Mg alloy, the maximum GFRG value was obtained for the following forming combinations: step depth 0.3 mm, feed rate 500 mm/min, spindle speed 700 rpm, and tool diameter 10 mm. Then, ANOVA was used to determine the importance of parameters on the responses, and it was discovered that the step depth has the greatest influence (68.78%) on GFRG value, followed by the feed rate (16.56%). The fracture behaviour of the Mg alloy was studied using fractographs. Later, FE simulation was used to validate the strain value obtained from experimentation and to investigate the effect of process parameters on responses. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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14 pages, 3820 KiB

Open AccessArticle

Mechanical Properties of σ-Phase and Its Effect on the Mechanical Properties of Austenitic Stainless Steel

by Peiheng Qiao, Jinyang Xie, Yong Jiang, Pengjie Tang, Bin Liang, Yilan Lu and Jianming Gong

Coatings 2022, 12(12), 1917; https://doi.org/10.3390/coatings12121917 - 7 Dec 2022

Cited by 1 | Viewed by 1871

Abstract

In this present paper, the mechanical properties of σ-phase and its effect on the mechanical properties of 304H austenitic stainless steel after servicing for about 8 years at 680–720 °C were studied by nano-indentation test, uniaxial tensile test, and impact test. The results [...] Read more.

In this present paper, the mechanical properties of σ-phase and its effect on the mechanical properties of 304H austenitic stainless steel after servicing for about 8 years at 680–720 °C were studied by nano-indentation test, uniaxial tensile test, and impact test. The results showed that the nano-hardness (H), Young’s modulus (E), strain hardening exponent (n), and yield strength (σ_y) of σ-phase were 14.95 GPa, 263 GPa, 0.78, and 2.42 GPa, respectively. The presence of σ-phase increased the hardness, yield strength, and tensile strength, but greatly reduced the elongation and impact toughness of the material. Full article

(This article belongs to the Special Issue Advances in Surface Engineering of Metals and Alloys)

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