| 1. |
- Alam, Md. Minhaj, et al.
(författare)
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Surface pore initiated fatigue failure in laser clad components
- 2013
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- A laser clad and machined cylindrical structural steel rod was fatigue tested under four-point bending load. The resulting fracture could be tracked back to a spherical surface pore in the Co-based coating. Due to an oxide inclusion, the pore was not identified by dye penetrant inspection. Two circular buckling strain patterns that were detected beside the pore at the surfaces after fracture confirm local plastic deformation prior to crack initiation. In order to calculate the stress field around the surface pore, linear elastic finite element analysis was carried out. For four-point bending load, a surface pore generally exceeds the maximum stress of a smooth rod as long as the pore is located within an azimuthal angle of ±55°, which was the case for the presented as well as for another pore initiated sample.
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| 2. |
- Harra, Juha, et al.
(författare)
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Characteristics of nFOG, an aerosol-based wet thin film coating technique
- 2018
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Ingår i: JCT Research. - : Springer Science and Business Media LLC. - 1547-0091 .- 2168-8028 .- 1935-3804. ; 15:3, s. 623-632
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Tidskriftsartikel (refereegranskat)abstract
- An atmospheric pressure aerosol-based wet thin film coating technique called the nFOG is characterized and applied in polymer film coatings. In the nFOG, a fog of droplets is formed by two air-assist atomizers oriented toward each other inside a deposition chamber. The droplets settle gravitationally and deposit on a substrate, forming a wet film. In this study, the continuous deposition mode of the nFOG is explored. We determined the size distribution of water droplets inside the chamber in a wide side range of 0.1–100 µm and on the substrate using aerosol measurement instruments and optical microscopy, respectively. The droplet size distribution was found to be bimodal with droplets of approximately 30–50 µm contributing the most to the mass of the formed wet film. The complementary measurement methods allow us to estimate the role of different droplet deposition mechanisms. The obtained results suggest that the deposition velocity of the droplets is lower than the calculated terminal settling velocity, likely due to the flow fields inside the chamber. Furthermore, the mass flux of the droplets onto the substrate is determined to be in the order of 1 g/m3s, corresponding to a wet film growth rate of 1 µm/s. Finally, the nFOG technique is demonstrated by preparing polymer films with thicknesses in the range of approximately 0.1–20 µm.
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| 3. |
- Juuti, Paxton, et al.
(författare)
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Achieving a slippery, liquid-infused porous surface with anti-icing properties by direct deposition of flame synthesized aerosol nanoparticles on a thermally fragile substrate
- 2017
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 110:16
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Tidskriftsartikel (refereegranskat)abstract
- Slippery, liquid-infused porous surfaces offer a promising route for producing omniphobic and anti-icing surfaces. Typically, these surfaces are made as a coating with expensive and time consuming assembly methods or with fluorinated films and oils. We report on a route for producing liquid-infused surfaces, which utilizes a liquid precursor fed oxygen-hydrogen flame to produce titania nanoparticles deposited directly on a low-density polyethylene film. This porous nanocoating, with thickness of several hundreds of nanometers, is then filled with silicone oil. The produced surfaces are shown to exhibit excellent anti-icing properties, with an ice adhesion strength of ∼12 kPa, which is an order of magnitude improvement when compared to the plain polyethylene film. The surface was also capable of maintaining this property even after cyclic icing testing.
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| 4. |
- Kiilakoski, Jarmo, et al.
(författare)
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Correction to : Process Parameter Impact on Suspension-HVOF-Sprayed Cr2O3 Coatings (Journal of Thermal Spray Technology, (2019), 28, 8, (1933-1944), 10.1007/s11666-019-00940-7)
- 2019
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Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 28:8
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Tidskriftsartikel (refereegranskat)abstract
- In the references section there is a correction to reference number 41. It should read as follows: V. Matikainen, S. Rubio Peregrina, N. Ojala, H. Koivuluoto, J. Schubert, S. HoudkovaÂŽ, and P. Vuoristo, Erosion Wear Performance of WC-10Co4Cr and Cr3C2– 25NiCr Coatings Sprayed with High-Velocity Thermal Spray Processes, Surf. Coat. Technol., 2019, 370, p 196- 212. © 2019, ASM International.
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| 5. |
- Kiilakoski, Jarkko, et al.
(författare)
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Process Parameter Impact on Suspension-HVOF-Sprayed Cr2O3 Coatings
- 2019
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 28:8, s. 1933-1944
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Tidskriftsartikel (refereegranskat)abstract
- Chromium oxide (Cr2O3) is commonly used as an atmospheric plasma-sprayed (APS) coating from powder feedstock in applications requiring resistance to sliding wear and corrosion, as well as amenability to texturing, e.g., in anilox rolls. Recently, high-velocity oxy-fuel spray methods involving suspension feedstock have been considered an extremely promising alternative to produce denser and more homogeneous chromium oxide coatings with lower as-sprayed surface roughness, higher hardness and potentially superior wear performance compared to conventional APS-sprayed coatings. In this study, the impact of process parameters namely auxiliary air cleaning nozzles and a transverse air curtain on suspension high-velocity oxy-fuel-sprayed Cr2O3 suspensions is presented. The produced coatings are characterized for their microstructure, mechanical properties and wear resistance by cavitation erosion. The results reveal the importance of optimized air nozzles and air curtain to achieve a vastly improved coating structure and performance.
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| 6. |
- Lamas, Javier
(författare)
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Analysis of laser arc hybrid welding experiments
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis is about the analysis of experimental results on the laser arc hybrid welding (LAHW) process as well as about the methodology and tools behind. Due to the high potential on weld penetration and welding speed, the industrial importance of LAHW techniques has been increasing in the recent years. However the massive use of them is constrained because of high investment costs, complexity and novelty. These obstacles provoke a lack of experienced operators and they desire a base of knowledge related to optimal parameters to obtain good quality welds. In this scenario, understanding of the physical LAHW phenomena has been proven useful for better control of the process,particularly to predict and avoid groups of parameters that can originate defects. For this reason, it is valuable to carry out experiments and to systematize the analysis methods.The presented work is focused on the impact of geometrical joint fit-up properties on the weld surface quality. The papers included here are organized as a comprehensive study of the effects and impact of various geometrical aspects of the laser-arc-workpiece arrangement on the surface quality of the welds, i.e. tracking from joint fit-up tolerances like gap width to critical weld shape aspects like undercuts via observation of fluid flow at the weld pool surface. Three frequent and critical geometrical aspects were identified from industrial edge preparation, namely gap width variations, vertical edgemismatch and vertical plate position to the laser-arc tool. These aspects can cause defects when the surface is bended or when the LAHW tool is automatically moved. Although in production they arise all simultaneously, to understand the respective contribution, systematic experiments were designed. These experiments were carried out to measure and surpass the stability threshold related to each aspect, to observe the flow behaviour and to evaluate the physical phenomena related to weld bead formation.The three Papers I, II, III describe a systematic methodology based on High Speed Imaging, HSI, on quantitative weld surface measurement obtained from a laser triangulation scanner and on statistical analysis of different experimental results. This methodology is based on the observation, measurement, automatic location and calculation of fundamental bead variables (top and root undercuts, reinforcement, melt pool length, pool width and flow speed, or mass balance) related to the melt flow.In Paper I, using a pulsed arc mode, the effects of increasing the standoff between the LAHW tool and the workpiece are described and a mechanism is identified to explain the flow behaviour and its consequences on the resulting weld pool shape. In Paper II, again using pulsed arc mode in LAHW, the effects of the vertical edge mismatch and of the gap width on the weld pool shape are described, again followed by a theoretical description. Paper III compares the pulsed arc mode with the CMT mode in LAHW,again for the effect of the gap width on the weld surface shape, in particular the top bridging phenomenon that was identified. Also these results are theoretically described, explaining the mechanisms via HSI.Altogether, the three papers comprise a theoretical description of the LAHW weld shape behaviour and weld quality depending on the fit-up tolerances, based on experimental evidence and analysis. From this chain of evidence and associated understanding, conclusions were drawn and practical guidelines were derived.
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| 7. |
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| 8. |
- Markocsan, Nicolaie, 1967-, et al.
(författare)
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Thermal spraying in Europe’s Nordic region
- 2007
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Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 16:4, s. 463-464
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Niemelä-Anttonen, Henna, et al.
(författare)
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Icephobicity of Slippery Liquid Infused Porous Surfaces under Multiple Freeze–Thaw and Ice Accretion–Detachment Cycles
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:20
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Tidskriftsartikel (refereegranskat)abstract
- Surface engineering can be used to prevent ice accumulation and adhesion in environments that deal with icing problems. One recent engineering approach, slippery liquid infused porous surfaces (SLIPS), comprises a smooth and slippery lubricating surface, where lubricant is trapped within the pores of a solid material to repel various substances, such as water and ice. However, it remains unclear whether the slippery surfaces retain their icephobic characteristics under the impact of supercooled water droplets or repeated freezing and melting cycles. Here, the icephobic properties of SLIPS are evaluated under multiple droplet freeze–thaw and ice accretion–detachment cycles and compared to hydrophobic and superhydrophobic surfaces. The experiments are designed to mimic real environmental conditions, thus, the icephobicity is investigated in icing wind tunnel, where ice accretion occurs through the impact of supercooled water droplets. The adhesion of ice remained extremely low, <10 kPa, which is four times lower than ice adhesion onto smooth fluoropolymer surfaces, even after repeated ice accretion–detachment cycles. Moreover, cyclic droplet freeze–thaw experiments provide insight into the effects of temperature cycling on SLIPS wettability, showing stable wetting performance. The results suggest liquid infused porous surfaces as a potential solution to icephobicity under challenging and variating environmental conditions.
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| 10. |
- Niemelä, Henna, et al.
(författare)
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Effects of multiple wetting incidents, shear and sliding friction on lubricant stability in SLIPS
- 2023
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Ingår i: Cold Regions Science and Technology. - : Elsevier B.V.. - 0165-232X .- 1872-7441. ; 211
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Tidskriftsartikel (refereegranskat)abstract
- Surface icing almost invariably derives from the precursory step of liquid water encountering the surface. Thus, slippery liquid infused porous surfaces, SLIPS, must possess steady wetting durability, and lubricant stability to function as a reliable hydro−/icephobic surface design especially in outdoor applications. Additionally, they should maintain their phobic performance under shear forces, and possess low sliding friction to act as a slippery, multirepellent surfaces. These characteristics are needed in variable applications ranging from moving and rotating blades to steady surfaces, operating in altering climate conditions. More profound durability testing is needed to examine the loss of surface functionality when the lubricant is depleted from the structure via various routes. In addition, the durability tests should be designed to serve the application-related purposes and thus, to reveal performance differences between slippery surfaces for further analysis and targeted end-use development. Here, we tested the wetting durability and stability of SLIPS with multicycle Wilhelmy plate by dipping the surfaces multiple times in water bath. Additionally, we examined the effects of centrifugal and friction-based shear stress to investigate the lubricant depletion from the structure. Tests that measure the durability and the stability of SLIPS designs are in great need in further developing functional slippery surfaces for real outdoor application coatings which encounter environmental stresses, e.g., wetting and icing. Acknowledging the material differences under specific stresses will guide designing the slippery surfaces towards more specific and functionable end-use applications
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| 11. |
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| 12. |
- Sadeghimeresht, Esmaeil, 1985-
(författare)
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Ni-based coatings for high temperature corrosion protection
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biomass/waste-fired boilers severely suffer from high temperature corrosion of critical load-bearing components, e.g. water-wall and superheater tubes, due to presence of Cl-containing corrosive species. Deposition of a dense and adherent Ni-based coating by high velocity air-fuel (HVAF) thermal spray technique is a promising approach to extend the component's lifetime and, hence, increase the thermal/electrical efficiency of the boilers. In this research, high temperature corrosion of candidate Ni-based coatings –Ni21Cr, Ni21Cr7AlY, Ni5Al, Ni21Cr9Mo, Ni21Cr9Mo-SiO2 – sprayed by HVAF has been investigated through detailed laboratory studies in ambient air, moisture and HCl-laden environments. The exposures were conducted at 600 °C for up to 168 h with and without presence of KCl salt. All coatings were highly protective in all environments in the absence of KCl due to formation of corresponding protective scales of alumina or chromia on the coating surface. When KCl was introduced, chromia-forming coatings degraded through a two-stage mechanism; 1) formation of K2CrO4 and Cl- followed by diffusion of Cl- through oxide grain boundaries, leading to formation of Cl2, metal chlorides as well as a nonprotective oxide, and 2) inward diffusion of the formed Cl2 through defects in the non-protective oxide, leading to metal chloride evaporation and breakaway oxidation. The corrosion behavior of the chromia-forming Ni21Cr coating was improved by addition of alloying elements such as Al and Mo. It was also shown that adding dispersed SiO2 further increased the corrosion resistance of the coatings. The oxide scale formed in the presence of SiO2 effectively suppressed Cl- ingress and lowered the corrosion rate, since the formed oxide was continuous, adherent andrich in Cr. The performance of the coatings in the complex Cl-containing environment was ranked as (from highest to lowest corrosion resistance); Ni21Cr9Mo-SiO2 > Ni21Cr7AlY > Ni5Al > Ni21Cr9Mo > Ni21Cr, confirming the enhanced corrosion protection of chromia-forming coatings in the presence of alloying elements and dispersed SiO2.
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| 13. |
- Vardelle, Armelle, et al.
(författare)
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Erratum to The 2016 Thermal Spray Roadmap
- 2017
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 26:5, s. 985-986
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Tidskriftsartikel (refereegranskat)
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| 14. |
- Vardelle, Armelle, et al.
(författare)
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The 2016 Thermal Spray Roadmap
- 2016
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 25:8, s. 1376-1440
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Tidskriftsartikel (refereegranskat)abstract
- Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications. © 2016, ASM International.
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| 15. |
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