Research

17 pages, 7465 KiB

Open AccessArticle

Microstructure and Corrosive Wear Properties of CoCrFeNiMn High-Entropy Alloy Coatings

by Haodong Wang, Jiajie Kang, Wen Yue, Guo Jin, Runjie Li, Yongkuan Zhou, Jian Liang and Yuyun Yang

Materials 2023, 16(1), 55; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010055 - 21 Dec 2022

Cited by 7 | Viewed by 1683

Abstract

In order to improve the wear resistance of offshore drilling equipment, CoCrFeNiMn high-entropy alloy coatings were prepared by cold spraying (CS) and high-speed oxygen fuel spraying (HVOF), and the coatings were subjected to vacuum heat treatment at different temperatures (500 °C, 700 °C [...] Read more.

In order to improve the wear resistance of offshore drilling equipment, CoCrFeNiMn high-entropy alloy coatings were prepared by cold spraying (CS) and high-speed oxygen fuel spraying (HVOF), and the coatings were subjected to vacuum heat treatment at different temperatures (500 °C, 700 °C and 900 °C). The friction and wear experiments of the coatings before and after vacuum heat treatment were carried out in simulated seawater drilling fluid. The results show that CoCrFeNiMn high-entropy alloy coatings prepared by CS and HVOF have dense structure and bond well with the substrate. After vacuum heat treatment, the main peaks of all oriented FCC phases are broadened and the peak strength is obviously enhanced. The two types of coatings achieve maximum hardness after vacuum heat treatment at 500 °C; the Vickers microhardness of CS-500 °C and HVOF-500 °C are 487.6 and 352.4 HV_0.1, respectively. The wear rates of the two coatings at room temperature are very close. CS and HVOF coatings both have the lowest wear rate after vacuum heat treatment at 500 °C. The CS-500 °C coating has the lowest wear rate of 0.2152 mm³ m⁻¹ N⁻¹, about 4/5 (0.2651 mm³ m⁻¹ N⁻¹) of the HVOF-500 °C coating. The wear rates and wear amounts of the two coatings heat-treated at 700 °C and 900 °C decrease due to the decrease in microhardness. The wear mechanisms of the coatings before and after vacuum heat treatment are adhesive wear, abrasive wear, fatigue wear and oxidation wear. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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14 pages, 3796 KiB

Open AccessArticle

Effect of Aging Treatment on the Precipitation Behavior of a Novel Al-Cu-Zr Cast Alloy

by Wu Wei, Rui Zuo, Da Xue, Shengping Wen, Yang Wu, Wei Shi, Xiaorong Zhou, Hui Huang, Xiaolan Wu, Kunyuan Gao, Li Rong and Zuoren Nie

Materials 2022, 15(22), 8163; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15228163 - 17 Nov 2022

Cited by 2 | Viewed by 1063

Abstract

A novel Al-Cu-Zr alloy is designed in this paper, which provides a method for further improving the strength of Al-Cu alloys. In this paper, the addition of the micro-alloying element Zr in Al-Cu alloy was studied. The effect of aging treatment on the [...] Read more.

A novel Al-Cu-Zr alloy is designed in this paper, which provides a method for further improving the strength of Al-Cu alloys. In this paper, the addition of the micro-alloying element Zr in Al-Cu alloy was studied. The effect of aging treatment on the mechanical properties and precipitation behavior of the alloy was studied. With the addition of Zr, Al₃Zr phases were formed in the alloy, which acts as obstacles to dislocation motion. In addition, Al₃Zr phases can be used as the nucleation site of θ′ phases to promote precipitation. All this can improve the strength of Al-Cu alloys. After one-step aging, corresponding to the highest hardness, the largest amount of θ′ phases were observed in the alloy matrix. By contrast, after two-step aging, the θ′ phases were finer, and a large amount of Guinier–Preston (GP) zones formed during the pre-aging step, which were transformed into denser and finer θ′ phases in the secondary aging step. After the same solution treatment (540 °C/12 h), undergoing 120 °C/4 h + 175 °C/10 h two-step aging, the ultimate tensile strength, yield strength, and elongation of the Al-Cu-Zr alloy were 398.7 MPa, 313.3 MPa, and 7.9%, respectively. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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19 pages, 11766 KiB

Open AccessArticle

Fabrication of the Zirconium Diboride-Reinforced Composites by a Combination of Planetary Ball Milling, Turbula Mixing and Spark Plasma Sintering

by Iwona Sulima, Paweł Hyjek and Marcin Podsiadło

Materials 2021, 14(14), 4056; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14144056 - 20 Jul 2021

Cited by 3 | Viewed by 1958

Abstract

The aim of this study was to carry out the consolidation of zirconium diboride-reinforced composites using the SPS technique. The effect of the adopted method of powder mixture preparation (mixing in Turbula or milling in a planetary mill) and of the reinforcing phase [...] Read more.

The aim of this study was to carry out the consolidation of zirconium diboride-reinforced composites using the SPS technique. The effect of the adopted method of powder mixture preparation (mixing in Turbula or milling in a planetary mill) and of the reinforcing phase content and sintering temperature on the microstructure, physical properties, strength and tribological properties of sintered composites was investigated. Experimental data showed that the maximum relative density of 94%–98% was obtained for the composites sintered at 1100 °C. Milling in a planetary mill was found to contribute to the homogeneous dispersion and reduced clustering of ZrB₂ particles in the steel matrix, improving in this way the properties of sintered steel + ZrB₂composites. Morphological and microstructural changes caused by the milling process in a planetary mill increase the value of Young’s modulus and improve the hardness, strength and wear resistance of steel + ZrB₂composites. Higher content of ZrB₂ in the steel matrix is also responsible for the improvement in Young’s modulus, hardness and abrasive wear resistance. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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11 pages, 5911 KiB

Open AccessArticle

Microstructure and Properties of TiB₂ Composites Produced by Spark Plasma Sintering with the Addition of Ti₅Si₃

by Agnieszka Twardowska, Marcin Podsiadło, Iwona Sulima, Krzysztof Bryła and Paweł Hyjek

Materials 2021, 14(14), 3812; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14143812 - 08 Jul 2021

Cited by 2 | Viewed by 1802

Abstract

Titanium diboride (TiB₂) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB₂-based composites of high density [...] Read more.

Titanium diboride (TiB₂) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB₂-based composites of high density with different sintering aids, among them titanium silicides. In this paper, Ti₅Si₃ is used as a sintering aid for the sintering of TiB₂/10 wt % Ti₅Si₃ and TiB₂/20 wt % Ti₅Si₃ composites at 1600 °C and 1700 °C for 10 min. The phase composition of the initial powders and produced composites was analyzed by the X-ray diffraction method using CuK_α radiation. The microstructure was examined using scanning electron microscopy, accompanied by energy-dispersive spectroscopy (EDS). The hardness was determined using a diamond indenter of Vickers geometry loaded at 9.81 N. Friction–wear properties were tested in the dry sliding test in a ball-on-disc configuration, using WC as a counterpart material. The major phases present in the TiB₂/Ti₅Si₃ composites were TiB₂ and Ti₅Si_3. Traces of TiC were also identified. The hardness of the TiB₂/Ti₅Si₃ composites was in the range of 1860–2056 HV1 and decreased with Ti₅Si₃ content, as well as the specific wear rate W_v. The coefficient of friction for the composites was in the range of 0.5–0.54, almost the same as for TiB₂ sinters. The main mechanism of wear was abrasive. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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14 pages, 6402 KiB

Open AccessArticle

The Extrusion and SPS of Zirconium–Copper Powders and Studies of Selected Mechanical Properties

by Tomasz Skrzekut, Grzegorz Boczkal, Adam Zwoliński, Piotr Noga, Lucyna Jaworska, Paweł Pałka and Marcin Podsiadło

Materials 2021, 14(13), 3560; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133560 - 25 Jun 2021

Cited by 1 | Viewed by 1489

Abstract

Zr-2.5Cu and Zr-10Cu powder mixtures were consolidated in the extrusion process and using the spark plasma sintering technique. In these studies, material tests were carried out in the fields of phase composition, microstructure, hardness and tensile strength for Zr-Cu materials at room temperature [...] Read more.

Zr-2.5Cu and Zr-10Cu powder mixtures were consolidated in the extrusion process and using the spark plasma sintering technique. In these studies, material tests were carried out in the fields of phase composition, microstructure, hardness and tensile strength for Zr-Cu materials at room temperature (RT) and 400 °C. Fractography analysis of materials at room temperature and 400 °C was carried out. The research took into account the anisotropy of the materials obtained in the extrusion process. For the nonequilibrium SPS process, ZrCu₂ and Cu₁₀Zr₇ intermetallic compounds formed in the material at sintering temperature. Extruded materials were composed mainly of α-Zr and ZrCu₂. The presence of intermetallic compounds affected the reduction in the strength properties of the tested materials. The highest strength value of 205 MPa was obtained for the extruded Zr-2.5Cu, for which the samples were cut in the direction of extrusion. For materials with 10 wt.% copper, more participation of the intermetallic phase was formed, which lowered the mechanical properties of the obtained materials. In addition to brittle intermetallic phases, the materials were characterized by residual porosity, which also reduced the strength properties. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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10 pages, 4255 KiB

Open AccessArticle

Novel High-Entropy Aluminide-Silicide Alloy

by Pavel Novák and Kateřina Nová

Materials 2021, 14(13), 3541; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133541 - 25 Jun 2021

Cited by 1 | Viewed by 1653

Abstract

Novel high-entropy (multi-principal elements) alloy based on Fe-Al-Si-Ni-Ti in equimolar proportions has been developed. The alloy powder obtained by mechanical alloying is composed of orthorhombic FeTiSi phase with the admixture of B2 FeAl. During spark plasma sintering of this powder, the FeSi phase [...] Read more.

Novel high-entropy (multi-principal elements) alloy based on Fe-Al-Si-Ni-Ti in equimolar proportions has been developed. The alloy powder obtained by mechanical alloying is composed of orthorhombic FeTiSi phase with the admixture of B2 FeAl. During spark plasma sintering of this powder, the FeSi phase is formed and the amount of FeAl phase increases at the expense of the FeTiSi phase. The material is characterized by a high compressive strength (approx. 1500 MPa) at room temperature, being brittle. At 800 °C, the alloy is plastically deformable, having a yield strength of 459 MPa. The wear resistance of the material is very good, comparable to the tool steel. During the wear test, the spallation of the FeSi particles from the wear track was observed locally. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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20 pages, 17671 KiB

Open AccessArticle

Investigation on Microstructure, Mechanical and Wear Properties of HVOF Sprayed Composite Coatings (WC–Co + CR) On Ductile Cast Iron

by Marzanna Ksiazek, Ilona Nejman and Lukasz Boron

Materials 2021, 14(12), 3282; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14123282 - 14 Jun 2021

Cited by 9 | Viewed by 2555

Abstract

Recent work indicates that the high-velocity oxy-fuel (HVOF) thermal spraying WC–Co coatings have been used to enhance the wear resistance of various engineering components in a variety of industrial environments. In the present work, WC–Co powder, containing Cr particles in an amount of [...] Read more.

Recent work indicates that the high-velocity oxy-fuel (HVOF) thermal spraying WC–Co coatings have been used to enhance the wear resistance of various engineering components in a variety of industrial environments. In the present work, WC–Co powder, containing Cr particles in an amount of 10%, was deposited on ductile cast iron with the HVOF thermal spray coating technique. An investigation was conducted to determine the role of Cr particles in the WC–Co coating produced with the HVOF technique on microstructure, mechanical, and wear properties in a system of type: WC-Co coating/ductile cast iron. The microstructure of the HVOF-sprayed WC–Co + Cr coating was characterised by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of a coating with low porosity, compact structure, and good adhesion to the substrate with a typical lamellar structure composed of fine molten Cr particles and finely fragmented WC grains embedded in a Co matrix, reaching the size of nanocrystalline. The scratch test was applied for the analysis of the adhesion of coatings to the substrate. The erosion behaviour and mechanism of material removal was studied and discussed based on microstructural examinations. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the WC–Co + Cr/ductile cast iron, as microhardness and erosion resistance of the coating. It was found that the addition of Cr particles to the WC–Co powder, which causes hardening of the binder phase is a key influence on increased mechanical and wear properties in the studied system. Additionally, due to the construction of nanostructured coatings, suitable proportion of hard and soft phases, the technique sprayed HVOF coatings have advantageous properties such as high density and good slurry erosion resistance. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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18 pages, 5806 KiB

Open AccessArticle

The Pressure Compaction of Zr-Nb Powder Mixtures and Selected Properties of Sintered and KOBO-Extruded Zr-xNb Materials

by Lucyna Jaworska, Tomasz Skrzekut, Michał Stępień, Paweł Pałka, Grzegorz Boczkal, Adam Zwoliński, Piotr Noga, Marcin Podsiadło, Radosław Wnuk and Paweł Ostachowski

Materials 2021, 14(12), 3172; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14123172 - 09 Jun 2021

Cited by 6 | Viewed by 1919

Abstract

Materials were obtained from commercial zirconium powders. 1 mass%, 2.5 mass% and 16 mass% of niobium powders were used as the reinforcing phase. The SPS method and the extrusion method classified as the SPD method were used. Relative density materials of up to [...] Read more.

Materials were obtained from commercial zirconium powders. 1 mass%, 2.5 mass% and 16 mass% of niobium powders were used as the reinforcing phase. The SPS method and the extrusion method classified as the SPD method were used. Relative density materials of up to 98% were obtained. The microstructure of the sintered Zr-xNb materials differs from that of the extruded materials. Due to the flammability of zirconium powders, no mechanical alloying was used; only mixing of zirconium and niobium powders in water and isopropyl alcohol. Niobium was grouped in clusters with an average niobium particle size of about 10 μm up to 20 μm. According to the Zr-Nb phase equilibrium system, the stable phase at RT was the hexagonal α-phase. The tests were carried out for materials without the additional annealing process. The effect of niobium as a β-Zr phase stabilizer is confirmed by XRD. Materials differed in their phase composition, and for both methods the β-Zr phase was present in obtained materials. A very favorable effect of niobium on the increase in corrosion resistance was observed, compared to the material obtained from the powder without the addition of niobium. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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12 pages, 4931 KiB

Open AccessArticle

Effect of Higher Silicon Content and Heat Treatment on Structure Evolution and High-Temperature Behaviour of Fe-28Al-15Si-2Mo Alloy

by Martin Švec, Věra Vodičková, Pavel Hanus, Petra Pazourková Prokopčáková, Libor Čamek and Jaromír Moravec

Materials 2021, 14(11), 3031; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14113031 - 02 Jun 2021

Cited by 4 | Viewed by 1657

Abstract

This paper describes the structure and properties of cast Fe₃Al-based alloy doped with 15 at. % of silicon and 2 at. % of molybdenum. The higher content of silicon is useful for the enhancement of high-temperature mechanical properties or corrosion resistance [...] Read more.

This paper describes the structure and properties of cast Fe₃Al-based alloy doped with 15 at. % of silicon and 2 at. % of molybdenum. The higher content of silicon is useful for the enhancement of high-temperature mechanical properties or corrosion resistance of iron aluminides but deteriorates their workability due to increased brittleness. It was found that the presence of both alloying elements leads to an increase of values of the high-temperature yield stress in compression. The heat treatment (annealing at 800 °C for 100 h) used for the achievement of phase stability causes the grain coarsening, so the values of the high-temperature yield stress in compression are lower at 600 °C and 700 °C in comparison to values measured for the as-cast state. This stabilization annealing significantly improves the workability/machinability of alloy. Furthermore, the higher silicon content positively affects the values of the thermal expansion coefficient that was found to be lower in the temperature range up to 600 °C compared to alloys with lower content of silicon. Full article

(This article belongs to the Special Issue Novel High-Temperature Materials: Preparation, Characterization, and Applications)

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