Research

15 pages, 4756 KiB

Open AccessArticle

Characterization of Cobalt-Based Stellite 6 Alloy Coating Fabricated by Laser-Engineered Net Shaping (LENS)

by Tomasz Durejko and Magdalena Łazińska

Materials 2021, 14(23), 7442; https://doi.org/10.3390/ma14237442 - 04 Dec 2021

Cited by 6 | Viewed by 2131

The results of microstructure and mechanical properties evaluation of a Stellite 6 (Co-6) alloy deposited on X22CrMoV12-1 substrate by the laser-engineered net shaping (LENS^TM) technology are presented in this paper. The Stellite 6 alloy is widely used in industry due to [...] Read more.

The results of microstructure and mechanical properties evaluation of a Stellite 6 (Co-6) alloy deposited on X22CrMoV12-1 substrate by the laser-engineered net shaping (LENS^TM) technology are presented in this paper. The Stellite 6 alloy is widely used in industry due to its excellent wear resistance at elevated temperatures and corrosive environments. Specific properties of this alloy are useful in many applications, e.g., as protective coatings in steam turbine components. In this area, the main problems are related to the fabrication of coatings on complex-shaped parts, the low metallurgical quality of obtained coatings, and its insufficient adhesion to a substrate. The results of recently performed investigations proved that the LENS technology is one of the most effective manufacturing techniques of the Co-6 alloy coatings (especially deposited on complex-shaped turbine parts). The microstructural and phase analyses of obtained Stellite 6 coatings were carried out by light microscopy techniques and X-ray diffraction analysis. A chemical homogeneity of Co-6 based layers and a fluctuation of chemical composition in coating–substrate zone after the laser deposition were analyzed using an energy dispersive X-ray spectrometer coupled with scanning electron microscopy. The room temperature strength and ductility of the LENS processed layers were determined in static bending tests. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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18 pages, 3576 KiB

Open AccessArticle

The Experimental and Numerical Research for Plastic Working of Nickel Matrix Composite Coatings

by Tomasz Dyl, Robert Starosta, Dariusz Rydz, Bartosz Koczurkiewicz and Wioletta Kuśmierska-Matyszczak

Materials 2020, 13(14), 3177; https://doi.org/10.3390/ma13143177 - 16 Jul 2020

Cited by 3 | Viewed by 1952

Abstract

In the machine, metallurgical, and shipbuilding industries, steel products with alloy and composite coatings based on nickel may be used. It is expedient to improve the physicochemical properties of the surface layer of products as they have a significant roughness value after thermal [...] Read more.

In the machine, metallurgical, and shipbuilding industries, steel products with alloy and composite coatings based on nickel may be used. It is expedient to improve the physicochemical properties of the surface layer of products as they have a significant roughness value after thermal spraying. It is therefore important to finish the layers applied by flame spraying, where machining is used for this purpose. However, it causes a loss of coating material, which is quite expensive. Therefore, in order to reduce costs and improve the quality of the surface layer, the finishing treatment of nickel-based coatings by means of plastic working is used. Two types of plastic working were proposed: rolling and burnishing. Numerical and experimental tests of the plastic processing of alloy coatings were carried out. The roughness of the coatings after rolling decreased to 1/25 and 30% strengthening of the alloy coating matrix was determined. After burnishing, roughness was reduced to 1/12 and the alloy coatings were strengthened by 25%. Plastic working by rolling and burnishing has a beneficial effect on the surface quality of the workpiece, not only by significantly improving the roughness, but also by increasing the strength properties of the surface layers. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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14 pages, 4699 KiB

Open AccessArticle

Heating Conditions Influence on Solidification of Inconel 625–WC System for Additive Manufacturing

by Jan Huebner, Paweł Rutkowski, Aleksandra Dębowska and Dariusz Kata

Materials 2020, 13(13), 2932; https://doi.org/10.3390/ma13132932 - 30 Jun 2020

Cited by 2 | Viewed by 1936

Abstract

In this study, an Inconel 625–tungsten carbide (WC) composite system was investigated by means of microstructure changes affected by both heating rate and WC content. In order to investigate how the system behaves while exposed to fast thermal processing, controlled melting using a [...] Read more.

In this study, an Inconel 625–tungsten carbide (WC) composite system was investigated by means of microstructure changes affected by both heating rate and WC content. In order to investigate how the system behaves while exposed to fast thermal processing, controlled melting using a differential thermal analysis (DTA) apparatus was performed on the powders. Two WC powders with different average grain size were used to obtain six compositions of Inconel 625–WC powder mixtures (10, 20, and 30 wt.% WC). They were analyzed under 10 and 30 °C/min heating rate in order to obtain composite samples. Results from DTA together with SEM/energy-dispersive X-ray spectroscopy (EDS) microstructural observations allowed observing material changes during solidification. Because of the extensive microsegregation of alloying elements to liquid and their reactions with C, which derived from dissolved WC, the formation of secondary phases with improved microhardness was possible. The collected results provide a better understanding of material behavior during intensive thermal processing which can be useful when designing materials for the laser additive manufacturing technique. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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12 pages, 2885 KiB

Open AccessArticle

Effect of Heat Treatment on Cr₂Nb Phase and Properties of Spark Plasma Sintered Cu-2Cr-1Nb Alloy

by Xueqian Lv, Zuming Liu, Ting Lei, Quan Li, Yake Ren, Xu Zhou and Zejie Zhang

Materials 2020, 13(12), 2860; https://doi.org/10.3390/ma13122860 - 25 Jun 2020

Cited by 8 | Viewed by 2445

Abstract

Achieving a good match between strength and conductivity is a challenge of the development of the high-performance Cu-Cr-Nb alloy for aerospace and fusion energy. The effect of heat treatment on Cr₂Nb phase, strength and conductivity of spark plasma sintered (SPSed) Cu-2Cr-1Nb [...] Read more.

Achieving a good match between strength and conductivity is a challenge of the development of the high-performance Cu-Cr-Nb alloy for aerospace and fusion energy. The effect of heat treatment on Cr₂Nb phase, strength and conductivity of spark plasma sintered (SPSed) Cu-2Cr-1Nb (at%) alloy was investigated. The results illustrated that Cr₂Nb phase of Cu-2Cr-1Nb alloy can be regulated by heat treatment, multi-scale Cr₂Nb phase with sizes of 0.10–0.50 μm, 30–100 nm and less than 30 nm was obtained, and the strength and conductivity were significantly increased after heat treatment at 500 °C for 2 h, the room temperature tensile strength and conductivity were 332 MPa and 86.7% IACS, 2.5% and 34.8% higher than those of as-SPSed alloy; the tensile strength at 700 °C was 76 MPa. Increasing heat treatment temperature and time, the tensile strength of the alloy was reduced by 1.5%, 4.3% and 12.3% after heat treatment at 500 °C, 700 °C and 950 °C for 72 h. The good match between strength and conductivity of Cu-Cr-Nb alloy was obtained by reducing the content of alloying elements (Cr and Nb) and microstructure regulation. This approach can be used to prepare structural/functional materials with excellent strength and conductivity. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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14 pages, 4850 KiB

Open AccessArticle

Superelastic Behavior of Ti-Nb Alloys Obtained by the Laser Engineered Net Shaping (LENS) Technique

by Damian Kalita, Łukasz Rogal, Piotr Bobrowski, Tomasz Durejko, Tomasz Czujko, Anna Antolak-Dudka, Eduard Cesari and Jan Dutkiewicz

Materials 2020, 13(12), 2827; https://doi.org/10.3390/ma13122827 - 23 Jun 2020

Cited by 10 | Viewed by 3288

Abstract

The effect of Nb content on microstructure, mechanical properties and superelasticity was investigated for a series of Ti-xNb alloys, fabricated by the laser engineered net shaping method, using elemental Ti and Nb powders. The microstructure of as-deposited materials consisted of columnar β-phase grains, [...] Read more.

The effect of Nb content on microstructure, mechanical properties and superelasticity was investigated for a series of Ti-xNb alloys, fabricated by the laser engineered net shaping method, using elemental Ti and Nb powders. The microstructure of as-deposited materials consisted of columnar β-phase grains, elongated in the built direction. However, due to the presence of undissolved Nb particles during the deposition process, an additional heat treatment was necessary. The observed changes in mechanical properties were explained in relation to the phase constituents and deformation mechanisms. Due to the elevated oxygen content in the investigated materials (2 at.%), the specific deformation mechanisms were observed at lower Nb content in comparison to the conventionally fabricated materials. This made it possible to conclude that oxygen increases the stability of the β phase in β–Ti alloys. For the first time, superelasticity was observed in Ti–Nb-based alloys fabricated by the additive manufacturing method. The highest recoverable strain of 3% was observed in Ti–19Nb alloy as a result of high elasticity and reverse martensitic transformation stress-induced during the loading. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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14 pages, 8722 KiB

Open AccessArticle

Microstructure and Residual Stresses of AA2519 Friction Stir Welded Joints under Different Heat Treatment Conditions

by Lucjan Śnieżek, Robert Kosturek, Marcin Wachowski and Bogusz Kania

Materials 2020, 13(4), 834; https://doi.org/10.3390/ma13040834 - 12 Feb 2020

Cited by 5 | Viewed by 1700

Abstract

The aim of this research was to investigate the effect of different heat treatment conditions of AA2519 friction stir welded joints on their microstructure and residual stresses. The following welding parameters have been used: 500 rpm tool rotation speed, 150 mm/min tool traverse [...] Read more.

The aim of this research was to investigate the effect of different heat treatment conditions of AA2519 friction stir welded joints on their microstructure and residual stresses. The following welding parameters have been used: 500 rpm tool rotation speed, 150 mm/min tool traverse speed, tool tilt angle 2°, pressure force 17 kN. The welded material was investigated in three different configurations: HT0, HT1, and HT2. The first type of weld (HT-0) was made using AA2519 alloy in non-precipitation hardened state and examined in such condition. The second type of weld (HT-1) has been performed on AA2519-T62, that corresponds to precipitation hardening condition. The last type of weld (HT2) was performed on annealed AA2519 and the obtained welds were subjected to the post-weld precipitation hardening process. The heat treatment was carried out in two stages: solution heat treatment (530 °C/2 h + cooling in cold water) and aging (165 °C/1 0 h). Residual stresses were measured using X-Ray diffraction patterns obtained from Bruker D8 Discover X-ray diffractometer utilizing the concepts of Euler cradle and polycapillary primary beam optics. The conducted research indicates that the best material properties: homogenous microstructure and uniform distribution of microhardness and compressive state of residual stresses were obtained for the HT-2 series samples subjected to heat treatment after the friction stir welding (FSW) process. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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13 pages, 10899 KiB

Open AccessArticle

A New Ultra-High-Strength AB83 Alloy by Combining Extrusion and Caliber Rolling

by Shuaiju Meng, Lishan Dong, Hui Yu, Lixin Huang, Haisheng Han, Weili Cheng, Jianhang Feng, Jingjing Wen, Zhongjie Li and Weimin Zhao

Materials 2020, 13(3), 709; https://doi.org/10.3390/ma13030709 - 05 Feb 2020

Cited by 3 | Viewed by 2046

Abstract

An exceptionally high-strength rare-earth-free Mg–8Al–3Bi (AB83) alloy was successfully fabricated via extrusion and caliber rolling. After three-pass caliber rolling, the homogenous microstructure of the as-extruded AB83 alloy was changed to a necklace-like bimodal structure consisting of ultra-fine dynamic recrystallized (DRXed) grains and microscale [...] Read more.

An exceptionally high-strength rare-earth-free Mg–8Al–3Bi (AB83) alloy was successfully fabricated via extrusion and caliber rolling. After three-pass caliber rolling, the homogenous microstructure of the as-extruded AB83 alloy was changed to a necklace-like bimodal structure consisting of ultra-fine dynamic recrystallized (DRXed) grains and microscale deformed grains. Additionally, both Mg₁₇Al₁₂ and Mg₃Bi₂ nanoprecipitates, undissolved microscale Mg₁₇Al₁₂, and Mg₃Bi₂ particles were dispersed in the matrix of caliber-rolled (CRed) AB83 alloy. The CRed AB83 sample demonstrated a slightly weakened basal texture, compared with that of the as-extruded sample. Consequently, CRed AB83 showed a tensile yield strength of 398 MPa, an ultimate tensile strength of 429 MPa, and an elongation of 11.8%. The superior mechanical properties of the caliber-rolled alloy were mainly originated from the combined effects of the necklace-like bimodal microstructure containing ultra-fine DRXed grains, the homogeneously distributed nanoprecipitates and microscale particles, as well as the slightly modified basal texture. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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12 pages, 5191 KiB

Open AccessArticle

Low Cycle Fatigue Properties of Sc-Modified AA2519-T62 Extrusion

by Robert Kosturek, Lucjan Śnieżek, Janusz Torzewski and Marcin Wachowski

Materials 2020, 13(1), 220; https://doi.org/10.3390/ma13010220 - 04 Jan 2020

Cited by 18 | Viewed by 2579

Abstract

This investigation presents the results of research on low cycle fatigue properties of Sc-modified AA2519-T62 extrusion. The basic mechanical properties of the investigated alloy have been established in the tensile test. The low cycle fatigue testing has been performed on five different levels [...] Read more.

This investigation presents the results of research on low cycle fatigue properties of Sc-modified AA2519-T62 extrusion. The basic mechanical properties of the investigated alloy have been established in the tensile test. The low cycle fatigue testing has been performed on five different levels of total strain amplitude: 0.4%; 0.5%; 0.6%; 0.7% and 0.8% with cycle asymmetry coefficient R = 0.1. For each level of total strain amplitude, the graphs of variations in stress amplitude and plastic strain amplitude in the number of cycles have been presented. The obtained results allowed to establish Ramberg-Osgood and Manson-Coffin-Basquin relationships. The established values of the cyclic strength coefficient and cyclic strain hardening exponent equal to k’ = 1518.1 MPa and n’ = 0.1702. Based on the Manscon-Coffin-Basquin equation, the values of the following parameters have been established: the fatigue strength coefficient σ’_f = 1489.8 MPa, the fatigue strength exponent b = −0.157, the fatigue ductility coefficient ε’_f = 0.4931 and the fatigue ductility exponent c = −1.01. The fatigue surfaces of samples tested on 0.4%, 0.6% and 0.8% of total strain amplitude have been subjected to scanning electron microscopy observations. The scanning electron microscopy observations of the fatigue surfaces revealed the presence of cracks in striations in the surrounding area with a high concentration of precipitates. It has been observed that larger Al₂Cu precipitates exhibit a higher tendency to fracture than smaller precipitates having a higher concentration of scandium and zirconium. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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12 pages, 7476 KiB

Open AccessArticle

Standard Hot Pressing as a Possible Solution to Obtain Dense K_0.5Na_0.5NbO₃ Ceramic Doped by Er₂O₃ and Yb₂O₃

by Paweł Rutkowski, Jan Huebner, Adrian Graboś, Dariusz Kata, Dariusz Grzybek and Bogdan Sapiński

Materials 2019, 12(24), 4171; https://doi.org/10.3390/ma12244171 - 12 Dec 2019

Cited by 5 | Viewed by 2388

Abstract

In this study, the influence of the addition of rare earth oxides on the phase composition and density of KNN piezoelectric ceramics was investigated. The initial powders of Na₂CO₃ and K₂CO₃ were dried at 150 °C for [...] Read more.

In this study, the influence of the addition of rare earth oxides on the phase composition and density of KNN piezoelectric ceramics was investigated. The initial powders of Na₂CO₃ and K₂CO₃ were dried at 150 °C for 2 h. Then, a powder mixture for synthesis was prepared by adding a stoichiometric amount of Nb₂O₅ and 5 and 10 wt % overabundance of Na₂CO₃. All powders were mixed by ball-milling for 24 h and synthesized at 950 °C. The phase composition of the reaction bed was checked by means of X-ray diffraction (XRD). It had an appearance of tetragonal and monoclinic K_0.5Na_0.5NbO₃ (KNN) phases. Then, 1 and 2 wt % of Er₂O₃ and Yb₂O₃, were added to the mixture. Green samples of 25 mm diameter and 3 mm thickness were prepared and sintered by hot pressing at 1000 °C for 2 h under 25 MPa pressure. The final samples were investigated via scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDS), XRD, Rietveld, and ultrasonic methods. Phase analysis showed tetragonal and orthorhombic KNN phases, and a contamination of (K₂CO₃·1.5H₂O) was present. The obtained KNN polycrystals had a relative density above 95%. Texturing of the material was confirmed as a result of hot pressing. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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21 pages, 8682 KiB

Open AccessArticle

The Influence of A Cross-Channel Extrusion Process on The Microstructure and Properties of Copper

by Radosław Łyszkowski, Magdalena Łazińska and Dariusz Zasada

Materials 2019, 12(23), 3995; https://doi.org/10.3390/ma12233995 - 02 Dec 2019

Cited by 3 | Viewed by 2825

Abstract

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The [...] Read more.

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The paper presents results of experimental trials of CCE process. Between one and eight passes of CCE with and without a BP were applied to pure copper billets to refine their initial coarse-grained microstructure at room temperature. It was found that processing by CCE results in the formation of a lamellar structure along the extruded axis and the fine-grained structure in the remaining volume. The material exhibited dynamic recrystallization, which results in the formation of 0.5- to 2-μm grains after one pass and 2- to 8-μm grains after four CCE passes. The fine-grained material had YS of 390-415 MPa. An increase in the microhardness from 70 to 130 HV02 after one pass and then a decrease after four passes were observed. This might indicate that secondary recrystallization and selective grain growth occur, because an exothermic peak (158.5 °C, 53 ± 2.1 J/mol) was observed during DSC (differential scanning calorimetry) testing. The resistivity of the once deformed copper significantly decreases, while its further processing causes the resistivity to increase. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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21 pages, 15579 KiB

Open AccessArticle

Effect of Ni/Si Mass Ratio and Thermomechanical Treatment on the Microstructure and Properties of Cu-Ni-Si Alloys

by Jiang Li, Guojie Huang, Xujun Mi, Lijun Peng, Haofeng Xie and Yonglin Kang

Materials 2019, 12(13), 2076; https://doi.org/10.3390/ma12132076 - 27 Jun 2019

Cited by 30 | Viewed by 3846

Abstract

The effect of the Ni/Si mass ratio and combined thermomechanical treatment on the microstructure and properties of ternary Cu-Ni-Si alloys is discussed systematically. The Cu-Ni-Si alloy with a Ni/Si mass ratio of 4–5 showed good comprehensive properties. Precipitates with disc-like shapes were confirmed [...] Read more.

The effect of the Ni/Si mass ratio and combined thermomechanical treatment on the microstructure and properties of ternary Cu-Ni-Si alloys is discussed systematically. The Cu-Ni-Si alloy with a Ni/Si mass ratio of 4–5 showed good comprehensive properties. Precipitates with disc-like shapes were confirmed as the Ni₂Si phase with orthorhombic structure through transmission electron microscopy, high-resolution transmission electron microscopy, and 3D atom probe characterization. After the appropriate thermomechanical treatment, the studied alloy with a Ni/Si mass ratio of 4.2 exhibited excellent mechanical properties: a hardness of 290 HV, tensile strength of 855 MPa, yield strength of 782 MPa, and elongation of 4.5%. Compared with other approaches, the thermomechanical treatment increased the hardness and strength without sacrificing electrical conductivity. Theoretical calculations indicated that the high strength was primarily attributed to the Orowan precipitation strengthening and secondarily ascribed to the work hardening, which were highly consistent with the experimental results. The appropriate Ni/Si mass ratio with a low content of Ni and Si atoms shows high strength and excellent electrical conductivity through combined thermomechanical treatment. This work provides a guideline for the design and preparation of multicomponent Cu-Ni-Si-X alloys with ultrahigh strength and excellent electrical conductivity. Full article

(This article belongs to the Special Issue High Performance Nonferrous Alloys: Composition, Microstructure and Properties)

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