| 1. |
- Fiandaca, Dario, et al.
(författare)
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An Integrated Approach for Structural Health Monitoring and Damage Detection of Bridges: An Experimental Assessment
- 2022
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:24
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Tidskriftsartikel (refereegranskat)abstract
- The issue of monitoring the structural condition of bridges is becoming a top priority worldwide. As is well known, any infrastructure undergoes a progressive deterioration of its structural conditions due to aging by normal service loads and environmental conditions. At the same time, it may suffer serious damages or collapse due to natural phenomena such as earthquakes or strong winds. For this reason, it is essential to rely on efficient and widespread monitoring techniques applied throughout the entire road network. This paper aims to introduce an integrated procedure for structural and material monitoring. With regard to structural monitoring, an innovative approach for monitoring based on Vehicle by Bridge Interaction (VBI) will be proposed. Furthermore, with regard to material monitoring, to evaluate concrete degradation, a non-invasive method based on the continuous monitoring of the pH, as well as chloride and sulfate ions concentration in the concrete, is presented.
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| 2. |
- Baiamonte, Lidia, et al.
(författare)
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Carbide-laden coatings deposited using a hand-held high-velocity air-fuel (HVAF) spray gun
- 2021
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 406
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Tidskriftsartikel (refereegranskat)abstract
- Driven by sustainability and cost considerations, there is growing interest in power generation utilizing renewable sources, especially biomass and waste. While premature degradation of power plant components due to corrosion is well-known, erosion can be a dominant damage mechanism in plants that use “pure” biomass with less corrosive elements like Cl, K, etc. Circulating fluidized bed (CFB) parts are prone to erosion-driven damage and demand periodic re-protection or replacement. In response to the above, this preliminary study evaluates a selection of complex carbide-based coatings to enhance protection against erosion to prolong service life of boiler components. Recognizing on-site coating requirements of real boiler applications, a specific focus is on evaluating performance of a hand-held high-velocity air-fuel (HVAF) spray gun and compare it with the current state-of-the-art high-velocity oxy-fuel (HVOF) deposition. Coatings developed by the above routes have been characterized with microstructural analyses, and their performance evaluated and ranked in an air-jet erosion rig at various impact angles.
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| 3. |
- Ganvir, Ashish, 1991-, et al.
(författare)
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Novel utilization of liquid feedstock in high velocity air fuel (HVAF) spraying to deposit solid lubricant reinforced wear resistant coatings
- 2021
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 295
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Tidskriftsartikel (refereegranskat)abstract
- The ability to axially inject liquid feedstock has encouraged the thermal spray research community to explore this concept to deposit coatings for various next generation functional applications. The current study explores the utilization of liquid feedstock in high velocity air fuel (HVAF) spraying to deposit solid lubricant reinforced wear resistant coatings for the first time. The study successfully demonstrates the use of a powder-suspension hybrid processing approach to incorporate a solid lubricant Boron Nitride (as suspension) in a wear resistant Cr3C2–NiCr (as powder) cermet matrix. Coatings were characterized using Scanning Electron Microscopy and Raman Spectroscopy to analyze their microstructure and phase constitution. The results show that the tribological performance of the hexagonal boron nitride (hBN)-incorporated composite coating was significantly better than the traditional powder-derived Cr3C2–NiCr coating. Such hBN-incorporated composite coatings are needed to improve the mechanical properties and enhance the overall tribological performance of metallic components used in various applications, especially at high temperature such as cylinder bore, pistons, deformation tools, etc. The limitations of liquid based lubricants at high temperature motivates the use of hBN reinforced composite coatings as it can form a protective solid lubrication tribo-film. The study concludes that the emerging HVAF technology can accommodate liquid feedstock and be successfully utilized to deposit hybrid powder-suspension composite coatings to create multi length scale microstructures which can be attractive for combining different tribological attributes in the same coatings system.
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| 4. |
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| 5. |
- Klement, Uta, 1962, et al.
(författare)
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Development of advanced hybrid materials with the help of pulse electrodeposition
- 2015
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Ingår i: Transactions of the Institute of Metal Finishing. - 1745-9192 .- 0020-2967. ; 93:6, s. 296-301
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Tidskriftsartikel (refereegranskat)abstract
- Pulse-electrodeposition has been applied to enhance properties of two different types of lightweight construction materials, a periodic cellular material (PCM) and a micro-sandwich. For the PCM, the deformation behaviour of the nanocrystalline Ni-18wt.%Fe sleeve material (bulk samples) has been investigated up to 548 K. The material exhibits plasticity of >30% fracture strain at higher temperatures compared to
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| 6. |
- Klement, Uta, 1962, et al.
(författare)
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Thermal stability of white layers intended as process-induced functional coatings
- 2020
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Ingår i: 12th Asia-Pacific Microscopy Conference. ; , s. 189-199
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Konferensbidrag (refereegranskat)abstract
- Hard turning and grinding are finishing processes for the manufacture of precision mechanical components. However, a major concern with respect to service performance (e.g. in bearing races receiving high contact stresses) is white layer (WL) formation on the component surface. WLs are microstructure alterations which are generally considered detrimental to fatigue life and wear resistance. But WLs can also be regarded as process-induced functional surfaces which result in improved wear resistance and produce compressive residual stresses which may significantly increase the component’s fatigue life. In fact, it was not clear if a favourable surface integrity can be produced in a controlled way using a set of selected process parameters until recently a predictive phenomenological model was presented by Hosseini [1]. The investigations on AISI 52100 have shown that different types of WL can be created that possess significantly different characteristics when one of the two driving forces, excessive heat or plastic deformation, can be isolated. The white layers would then be differentiated into thermally-induced WL (T-WL) and mechanically induced WL (M-WL). Due to their nanocrystalline microstructure (Fig. 1), no or severely reduced retained austenite content, compressive residual stresses and lack of dark layer, M-WLs are expected to have advantageous properties. For them to also have industrial relevance as process-induced functional coatings, the WL would have to endure elevated temperatures as well as external dynamic/static loading as most applications would induce them. However, the intrinsic instability of the nanostructure in the M-WLs may compromise the gain in properties (compressive stresses, hardness, etc.) by the occurrence of grain growth during exposure to elevated temperatures. Thermal stability is therefore a fundamental materials issue for these process-induces functional coatings and the investigation is the prime task in this study, although the applied loads (dynamic/static) will also play an important role in destabilizing the microstructure. T-WL and M-WLs were investigated in detail by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). For determining the thermal stability, both types of WL were also investigated after heat treatments at 235, 335 and 435°C using OM and SEM. Furthermore, the hardness of the structures was evaluated at different temperatures. The microstructural characterization indicated a clear decomposition of the WLs at elevated temperatures, transforming from not being able to resolve any features at all at room temperature and 235°C, to being able to detect features present in the structure after annealing at 335 and 435°C, respectively (compare Fig. 2). At the highest temperature, the primary (Fe, Cr)3C-carbides are more visible, whereas at the lowest temperature even such carbides were difficult to detect using SEM as they are embedded in the WL. Given, the major differences between T-WL and M-WL, the grain growth process will also be significantly different. In T-WLs, Hosseini et al. [2] reported about 13 vol.% of retained austenite, while in the case of M-WLs, no austenite could be detected. That means that during tempering, in T-WLs the austenite will decompose into ferrite and cementite, whereas in the M-WLs, with increasing tempering temperature, alloy partitioning of e.g. Cr will allow for transformation from the as obtained non-stoichiometric carbides to stoichiometric carbides. Cr, Mn and Mo partitioning inside carbides at temperatures of about 450°C was also reported by Clarke et al. [3]. XRD and TEM analyses are used for a better understanding of the thermal stability of such structures and for determination of the microstructure constituents. The microstructural changes in the WLs are also accompanied by a decrease in hardness with increasing annealing temperature. Our investigation revealed that the M-WL as compared to T-WL possess a ~50 HV higher hardness at 235°C and 335°C. However, at 435°C, the differences are equalized between the WLs. Summary and conclusion: · It can clearly be shown that with increasing temperature, a larger portion of the WLs decompose. This occurs independent of if the WLs are mechanically or thermally induced. · The hardness measurements showed that the M-WL had initially a higher hardness than the T-WL near the machined surface. However, with increasing annealing temperature, the hardness values between them equalized and reached the same hardness. · Both M-WL and T-WL seem to be stable up to at least 235°C. This is promising for a potential application of M-WLs as functional coatings as temperatures above 200°C are not expected in intended applications.
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| 7. |
- Kovalska, Natalia, et al.
(författare)
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Electrodeposition of Soft Magnetic Fe-W-P Alloy Coatings from an Acidic Electrolyte
- 2023
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Ingår i: Coatings. - 2079-6412. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Fe-W-P coatings were deposited from a newly developed electrolytic bath. The effect of plating parameters, such as electrolyte current density and pH has been studied. It was found that the pH has a very strong effect on the phosphorous content of the coatings. Metallic-like, non-powdery alloys of Fe-W-P deposits with no cracks (lowly stressed) can be obtained at a lower pH (<3), exhibiting high phosphorus (up to 13 at.%) and low tungsten (6 at.%) contents. At a higher pH (>3), the composition changes to low phosphorus and high tungsten content, showing a matte, greyish, and rough surface. The applied current density also influences the morphology and the amount of phosphorous content. The deposits showed an amorphous structure for all samples with soft ferromagnetic properties.
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| 8. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Incorporation of graphene nano platelets in suspension plasma sprayed alumina coatings for improved tribological properties
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 570
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Tidskriftsartikel (refereegranskat)abstract
- Graphene possesses high fracture toughness and excellent lubrication properties, which can be exploited to enhance tribological performance of coating systems utilized to combat wear. In this work, suspension plasma spray (SPS) process was employed to deposit a composite, graphene nano-platelets (GNP) incorporated alumina coating. For comparison, monolithic alumina was also deposited utilizing identical spray conditions. The as-deposited coatings were characterized in detail for their microstructure, porosity content, hardness, fracture toughness and phase composition. Raman analysis of the as-deposited composite coating confirmed retention of GNP. The composite coating also showed good microstructural integrity, comparable porosity, higher fracture toughness and similar alumina phase composition as the monolithic alumina coating. The as-deposited coatings were subjected to dry sliding wear tests. The GNP incorporated composite coating showed lower CoF and lower specific wear rate than the pure alumina coating. Additionally, the counter surface also showed a lower wear rate in case of the composite coating. Post-wear analysis performed by SEM/EDS showed differences in the coating wear track and in the ball wear track of monolithic and composite coatings. Furthermore, Raman analysis in the wear track of composite coating confirmed the presence of GNP. The micro-indentation and wear test results indicate that the presence of GNP in the composite coating aided in improving fracture toughness, lowering CoF and specific wear rate compared to the monolithic coating. Results from this work demonstrated retention of GNP in an SPS processed coating, which can be further exploited to design superior wear-resistant coatings.
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| 9. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Investigating Load-dependent Wear Behavior and Degradation Mechanisms in Cr3C2-NiCr coatings deposited by HVAF and HVOF
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 4595-4609
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Tidskriftsartikel (refereegranskat)abstract
- Wear resistant coatings that comply with non-toxic environment goals are highly desirable. Cr3C2-NiCr is a promising alternative to the toxic, ‘Co’- containing WC-Co coatings to mitigate wear. The purpose of this study was to examine the suitability of Cr3C2-NiCr coatings for automotive brake disc application by systematically investigating their dry sliding wear behavior at different test conditions. Therefore, High Velocity Air Fuel (HVAF) and High Velocity Oxy Fuel (HVOF) were employed to deposit Cr3C2-NiCr coatings. The powder feedstock and as-deposited Cr3C2-NiCr coatings were characterized for their microstructure and phase composition using SEM and XRD. Mechanical properties (hardness, fracture toughness), porosity and surface topography of the as-deposited coatings were evaluated. The coatings were subjected to sliding wear tests at different normal loads (5 N, 10 N and 15 N) using alumina ball as the counter surface. Coefficient of friction (CoF) evolution of HVAF and HVOF deposited coatings, along with their wear performance, was obtained for different normal load conditions. The wear performance ranking of HVAF and HVOF processed coatings was influenced by the test conditions, with HVAF coatings demonstrating better wear resistance than HVOF coatings at harsh test conditions and the HVOF coatings performing better under mild wear test conditions. Detailed post-wear analysis of worn coatings, the alumina ball counter-body and the resulting debris was performed to reveal the degradation mechanisms at different test conditions. Findings from this work provide new insights into the desirable microstructural features to mitigate wear, which can be further exploited to deposit wear-resistant coatings.
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| 10. |
- Mahade, Satyapal, 1987-, et al.
(författare)
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Novel suspension route to incorporate graphene nano-platelets in HVAF-sprayed Cr3C2-NiCr coatings for superior wear performance
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 13, s. 498-512
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Tidskriftsartikel (refereegranskat)abstract
- Graphene nano platelets (GNP) have several attractive properties, including excellent lubricity that can be used to develop wear-resistant coatings. Thermally sprayed chromium carbide-nickel chromium (Cr3C2-NiCr) coatings are widely employed to impart wear resistance to engineering components. This work attempts to improve the wear resistance of high velocity air fuel (HVAF) sprayed Cr3C2-NiCr coatings by incorporating GNP using a hybrid approach in which Cr3C2-NiCr (powder) and GNP (suspension) are co-axially injected. Two different powder-to-suspension delivery ratios were employed in this study that utilizes a liquid feedstock in tandem with a HVAF system. Furthermore, for comparison, a pure (without graphene) Cr3C2-NiCr reference coating was deposited by the HVAF process using identical spray parameters. The as-sprayed coatings were characterized for their microstructure and phase constitution by SEM/EDS and X-Ray Diffraction. Mechanical properties such as hardness and fracture toughness were evaluated using micro-indentation technique. The hybrid coatings were subjected to dry sliding wear tests and wear performance was compared with reference Cr3C2-NiCr. The GNP incorporated hybrid coatings exhibited lower CoF and lower wear rates than the reference Cr3C2-NiCr coating. Post wear SEM/EDS analysis revealed different wear mechanisms predominant in the investigated coatings. Utilizing the above as a case study, this work provides key insights into a new approach to produce GNP incorporated coatings for mitigating wear.
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