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Heat treatment
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Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 8-16, April 29–May 1, 2024,
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All solid-state sodium-ion batteries (ASS-SIBs) have great potential for application to large-scale energy storage devices due to their safety advantages by avoiding flammable organics and the abundance of sodium. In this study, plasma spraying was used to deposit Na 3 Zr 2 Si 2 PO 12 (NZSP) electrolyte for assembling high performance ASS-SIBs. NZSP electrolyte layers were deposited at different spray conditions using NZSP powders in different particle sizes. The factors influencing the microstructure and compositions of NZSP layers were examined by characterizing the compositions of splat and cross-sectional microstructures of the deposits. It was found that the preferential evaporation loss of Na and P elements occurs severely to result in a large composition deviation from initial powders and spray particle size is key factor which dominates their evaporation loss. The APS NZSP electrolytes present a dense microstructure with well bonded splats which is attributed to low melting point of NZSP. The apparent porosity of the as-sprayed NZSPs was lower than 3 %. The effect of annealing on the microstructure of APS NZSP was also investigated. The performance of typical APS NZSP was also evaluated by assembling an ASS-SIB battery with APS NaxCoO2 (NCO), Na 3 Zr 2 Si 2 PO 12 (NZSP) and Li 4 Ti 5 O 12 (LTO) as cathode, electrolyte and anode, respectively. Results showed that columnar-structured grains with a chemical inter-splat bonding were formed across the interfaces between electrodes and electrolyte. There is no evidence of inter-diffusion of zirconium, cobalt and silicon across the NCO/NZSP interface. With the preliminary battery, the solid electrolyte exhibited an ionic conductivity of 1.21 × 10 -4 S cm -1 at 200 o C. The SIB can operate at 2.5 V with a capacity of 10.5 mA h g -1 at current density of 37.4 μA cm -2 .
Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 376-381, April 29–May 1, 2024,
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Bond coats are used to protect the superalloy from oxidation and to serve as a bond between the ceramic thermal barrier coating (TBC) layer and the superalloy. During high temperature exposures, a thermally grown oxide (TGO) layer forms between the bond coat and the topcoat due to oxygen diffusion, leading to coating failure in the components. This study aimed to investigate the microstructure evolution of three TBCs with different cold-sprayed bond coat alloys after undergoing isothermal heat treatments. The TBCs were heat treated at 1100 °C for durations of 12, 25, and 50 hours to observe the effects of temperature on the microstructure and phase distribution. The microstructure of heat-treated bond coat alloys was examined using scanning electron microscopy and x-ray diffraction. The findings are discussed in relation to the characteristics of the coating alloy and the application process.
Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 418-426, April 29–May 1, 2024,
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Surface coatings play a pivotal role in enhancing mechanical and functional properties of various materials. High Entropy Alloy (HEA) annealed coatings have garnered significant interest due to their potential to improve wear resistance and overall durability. This research presents a comprehensive study focused on the characterization of HEA annealed coatings. It focuses on evaluating their roughness and wear performance. In this research, a systematic approach is adopted to assess the effects of annealing on coating surface properties. The investigation begins with the deposition of the Al 0.1-0.5 CoCrCuFeNi and MnCoCrCuFeNi coatings using a well-established cold spray (CS) technique, followed by a controlled annealing process. The coating surface roughness is analyzed using profilometry and microscopy techniques. This offers insights into the changes induced by annealing. The wear performance of the annealed coatings is evaluated through tribological tests.
Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 724-731, April 29–May 1, 2024,
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Revealed as a process for surface functionalization and repair, cold spray is currently used as a reliable additive manufacturing process thanks to its ability to fabricate dense solid-state deposits with high deposition efficiency. However, cold-sprayed deposits generally present limited mechanical and structural properties due to manufacturing defects such as microporosities and weak interfacial particle bonding. As solutions, post-processing methods such as heat treatment or hot isostatic pressing are proposed to reduce manufacturing defects and optimize final deposit properties. This paper investigates the heat treatment effect on structural and mechanical features of cold sprayed 3D Aluminium part by comparing deposits properties evolution with the additive growth in the as sprayed and heat-treated states. Thus, a study is carried out to identify the right heat treatment conditions for optimizing deposits properties.
Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 732-742, April 29–May 1, 2024,
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Cold spray is a solid-state metal powder deposition technique that has proven to be highly effective in depositing a wide range of metals, including aluminum and its alloys. However, higher strength, heat treatable Al alloys appear to exhibit variable deposition efficiencies and responses to heat treatments designed to increase ductility. This work is aimed at understanding the sources of these variabilities. In this study, 6061 (0.9% Mg, 0.6% Si, 0.3% Cu, 0.1% Cr, 0.1% Fe) alloy is compared to 7075 (6% Zn, 1.6% Cu, 2.4% Mg, 0.2% Cr, 0.3% Fe) alloy. These are common heat treatable alloys, but they exhibit quite different cold spray characteristics. Generally, 7075 is more problematic in terms of deposition efficiency and the mechanical properties after heat treatment. The alloys were processed under various cold spray conditions, including laser assisted cold spray designed to soften the 7075, and subjected to heat treatments intended to increase ductility. The microstructure and mechanical properties of the as sprayed and heat-treated coatings were characterized and compared. The results of this investigation will reveal possible mechanisms explaining the different cold spray behaviors and some suggestions will be proposed to overcome the problems associated with 7075.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 30-37, May 22–25, 2023,
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The Cold spray (CS) is a promising solid-state additive manufacturing method. The interesting physics involved in the CS process including cold, high strain rate, adiabatic and severe plastic deformation results in a unique and complex structure of CS deposits at different length scales that directly determines the properties of the deposits. Therefore process- structure properties (performance) (PSP) linkages explorations are pivotal. Integrated computational materials engineering (ICME) methods in complement with experimental analyses are required to evaluate materials properties and behaviour in PSP links exploration. Finite element modelling is used to simulate the thermomechanical response of materials and evolution of field variables in CS, i.e stress, strain, strain rate, and temperature, at structural scales. Molecular dynamics modellings of nano-particle impact have provided useful insights into atomic-scale phenomena of individual particle impact while the modelling of microstructure evolution in micro and mesoscale has yet to be investigated. In this study, we developed and implemented a thermodynamic phase field simulation method to capture the structure evolution of CS composite Ni-Ti deposit upon post-spray heat treatment (PSHT) in microstructure scale. The external or internal stimuli such as heat and strain either generated in the system because of phase transformation or stored as internal energy upon CS process are accounted for. The interface mobility and microstructure development are calculated by minimization of Gibbs free energy of the system. The comparison of the simulated microstructure with experimental results confirms that the phase field modelling precisely predicts the microstructure evolution of the CS deposits upon PSHT.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 91-97, May 22–25, 2023,
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In conventional powder processing, there has been considerable work on classifying feedstock powders based on particle size distribution, morphology, microstructure and composition, since these influence processability and final properties. Cold spray is a new application for powders and conventional characterization may be insufficient to assess powder cold sprayability. In particular, metallic powders have an oxide layer, which breaks during impact with the substrate or with another coating layer during cold spray; this fragmentation facilitates bonding. It has been suggested that the thickness of the oxide layer can influence the mechanism of fragmentation; thicker oxides are easier to remove, revealing clean metal surfaces that can metallurgically bond. Consequently, not all high-purity powders or powders that are stored in ambient conditions have the potential to give good coating properties after cold-spray. This work focuses on surface oxidation of the powders, characterizing the variation of oxide film aspects with size and composition of nominally pure copper powders using X-ray Photoelectron Spectroscopy (XPS). The results indicate the presence of Cu (I) and Cu (II) oxide species on the surface of as-received, naturally aged and heat-treated powders; their thickness is determined using the depth profiling feature.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 242-249, May 22–25, 2023,
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The performance of two distinct coating materials under alumina particle impingement was tested in this study. CrMnFeCoNi and WC-Ni coatings were applied to 2205 duplex stainless steel substrates using cold spray method with nitrogen as the process gas. In between the substrate and the high entropy alloy coating, an interlayer coating of 316 stainless steel was used. The presence of WC particles in the WC-Ni composite coatings was confirmed by SEM cross sectional inspection. Following deposition, the coatings were heat treated in an air furnace. The influence of heat treatment holding time on the WC-Ni coatings was studied using chemical analysis by X-ray diffraction. Heat treatments peak temperatures for the WC/Ni- Ni and high entropy alloy coatings were 600°C and 550°C, respectively. Coatings microhardness and porosity volume fraction were measured for all the samples. The HEA coating outperformed the WC/Ni-Ni hardness but exhibited a higher level of porosity. The coatings were then subjected to erosion experiments using alumina particles with variable impact angles (30°, 60°, and 90°). To compare the different materials, an average erosion value was calculated for each target specimen. The WC/Ni-Ni as-sprayed coating was the most effective against a 60° impingement angle. The HEA coating, on the other hand, demonstrated greater resistance to impact angles of 30° and 90°. SEM was utilized to examine the eroded areas and determine the main mechanisms of erosion.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 288-294, May 22–25, 2023,
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Successful cold spray of tool steels and other hard steels would unlock several opportunities, including the repair of molds as well as ships and heavy industry components. However, the high hardness of typical atomized steel powders strongly limits their cold sprayability. It has been recently demonstrated that heat treatment in a rotating furnace can significantly improve H13 cold sprayability via softening and agglomeration. In this work, this powder modification method is extended to a range of transformation hardenable steels: 4340, SS420, A588, 1040 and P20. The results show that powder heat treatment improves the powder deposition efficiency and the quality of the final cold sprayed coating, probably as the result of the decreased powder micro-hardness. The effects of the powder heat treatment atmosphere, a key parameter, will also be presented and discussed.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 365-372, May 22–25, 2023,
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Ni/Co-based alloys have been widely employed as bond coats (BCs) in thermal barrier coatings (TBCs) to provide oxidation resistance through the formation of a dense thermally grown oxide (TGO) layer. TGO thickening is a major contributor to TBC failure. Conventional approaches to minimize its growth have included refinement/optimization of the BC composition, deposition techniques, and post-treatments. However, these approaches have only led to incremental improvements in TBC performance and do not directly address the effect of the thin interfacial oxide layer on the TBC lifetime. In a shift from conventional thinking, the development of an Al 4 C 3 -Ni alloy composite BC aims to overcome the challenges generated by current TGOs. Post-deposition heat treatment tailors the coating microstructure to form a continuous internal carbide network. At elevated temperatures, the Al 4 C 3 preferentially oxidizes to form an interlacing protective Al 2 O 3 “root” that provides better TGO anchoring and reduces TBC thermal mismatch with the substrate. In this paper, the coatings were manufactured through gas-shrouded plasma spraying using various parameters to optimize the degree of inflight carbide dissolution and minimize the extent of coating porosity and cracking. XRD and carbon analysis were performed on the coatings and the microstructure was observed using SEM. Differences between coatings are discussed in relation to the spraying parameters.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 373-379, May 22–25, 2023,
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Conventionally, bulk WC and Cr 3 C 2 -based carbide compositions have been used independently of each other. However, recent investigations have begun to explore combining these carbides together within the same composite/hardmetal coating system. This research builds on earlier work characterising 42%wt% WC-42%wt% Cr 3 C 2 - 16%wt% Ni coatings sprayed under “low”, “medium” and “high” thermal input conditions, to assess their compositions and microstructures after heat treatment in air at 900°C for up to 30 days. Coatings were deposited by HVOF, Ar-He and Ar- H 2 shrouded plasmas respectively, onto Alloy 625 substrates with Ni20Cr bond-coats and top-coats. The coating compositions and lattice parameters were quantified by Rietveld peak fitting of XRD patterns. The microstructures were analysed from cross sectional backscatter electron micrographs. Rapid phase development occurred within the first five days, beyond which the compositions and microstructures remained stable. The microstructures retained extremely fine, sub-micron grain sizes, while the carbide phases exhibited high degrees of metastable alloying, even after 30 days at 900°C. The coating compositions are discussed, and a mechanism proposed to account for the rate of development and overall metastable microstructure.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 400-407, May 22–25, 2023,
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The application of cold spray (CS) for additive manufacturing (CSAM) of structural components using metallic materials has recently attracted much attention. However, there are limited reports on developing thick deposits or components with high entropy alloys (HEAs) via CSAM and investigating the microstructural evolution and mechanical properties after deposition and subsequent annealing heat-treatment. This work investigated the microstructure and mechanical properties of asdeposited and heat-treated thick CoCrFeNiMn HEA deposit fabricated via CSAM. The microstructure of the HEA deposit and after heat-treatment were characterised using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and x-ray diffraction (XRD). The microstructural analysis reveals heterogeneous grain size distribution with ultrafine grains at the particle-particle interfacial regions and coarse grains at the particle interiors in the as-deposited sample. The as-deposited sample, characterised by moderate porosity, was consolidated following the heat treatment at different temperatures. Additionally, increasing the temperature increases grain sizes resulting from static recovery and recrystallisation, with annealing twin formed at higher temperatures. Most notably, phase decomposition of the deposit microstructure occurs at 600 ºC, with Cr-rich phase particles formed at regions of high dislocations and grain boundaries. Nano-and micro-hardness and tensile testing of micro-flat dogbones samples were performed on the as-deposited and heattreated samples. The effect of heat-treatment on the microstructure and mechanical properties of the cold-sprayed HEA deposit were analysed and discussed.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 450-457, May 22–25, 2023,
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A micro-plasma system was investigated for its capability in additive manufacturing (AM). Micro-plasma AM system has the advantage of lower cost and higher deposition rate over the laser-based AM systems, and generates leaner and cleaner weld deposit than other arc-based AM systems. However, the microplasma system is complex and involves a large number of process variables. In this study, the effects of two arc and wire feed modes on dimensional consistency and hardness were firstly examined. Subsequently, one set of the specimens was further subjected to oxidation tests and the results were compared to that from conventional wrought Inconel 718. It was found that all four processes could produce crack free samples without measurable distortion. Some surface discoloration was observed, ranging from light straw to a purple tint. After heat treatment, the hardness of the samples varies from 403 to 440 HV, with the transverse surface showing slightly lower hardness values. The oxidation tests at 900 °C yielded similar weight change for AM Inconel 718 and its counterpart wrought alloy; however, the rate constant for wrought alloy was slightly higher. Microstructural analysis with SEM and EDS revealed a dendritic structure in the AM Inconel 718 and the presence of Nb-rich compounds in the interdendritic region. The polycrystal grain structure was not delineated in AM material as that in wrought 718. With the increase of exposure time, the oxide layer continues to increase at a higher rate, along with a sublayer of Ni 3 Nb above the metal substrate. In addition, after 200 hours, the wrought alloy developed porous chromia, while AM material exhibited uneven oxide thickness. In consideration of all aspects of the evaluation carried out thus far, it is concluded that the AM material produced by micro-plasma process is equivalent to wrought material in mechanical properties and oxidation performance.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 458-465, May 22–25, 2023,
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Thermal spray processes benefit from workpiece cooling to prevent overheating of the substrate and to retain metallurgical properties (e.g., temper). Cold-gas “plume quenching” is a plume-targeting cooling technique, where an argon curtain is directed laterally above the substrate surface to re-direct high temperature gases without impacting particle motion. However, there has been little investigation of its effect on the molten particles and the resulting coating properties. This study examined high- and medium- density tantalum and nickel coatings, fabricated by Controlled Atmosphere Plasma Spray with and without plume quenching on aluminum and titanium substrates. To compare the effect of plume quenching, the deposition efficiency was calculated through coating mass gain, and the coating density, stiffness, and adhesion were measured. The tantalum and nickel coatings were largely unaffected by plume quenching with respect to deposition efficiencies, coating density, adhesion, and stiffness. These results indicate that a plume quench could be used without affecting the coating properties for high- and medium-density metals while providing the benefit of substrate cooling that increases with higher plume quench gas flow rates.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 604-609, May 22–25, 2023,
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The previous results have shown that dense bismuth oxidebased electrolytes can be fabricated simply by plasma spraying owing to their low melting point. In this study, the Bi 2 O 3 – Er 2 O 3 –WO 3 electrolyte of high ionic conductivity was deposited by the cost-effective plasma spraying to assemble the SOFC for examining its electrochemical performance. The SOFC cell consisted of FeCr 24.5 metal support, NiO-YSZ anode, 10 mol% scandium oxide-stabilized zirconium oxide (ScSZ) electrolyte, (Bi 2 O 3 ) 0.705 (Er 2 O 3 ) 0.245 (WO 3 ) 0.05 (EWSB) electrolyte, and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode. The ScSZ electrolyte interlayer was introduced between the anode and EWSB electrolyte to hinder the reduction of EWSB in the anode environment. NiO-YSZ, ScSZ, EWSB, and LSCF were deposited by plasma spraying on the metal support which was prepared by a press-forming-sintering process. The NiO-YSZ/ ScSZ/ EWSB/ LSCF single cell assembled with the as-sprayed ScSZ presented an open circuit potential of 0.90V at 600 °C and the maximum power density of 1130 mW cm -2 at 750 °C, 450 mW cm -2 at 650 °C, and 128 mW cm -2 at 550 °C. The plasma sprayed ScSZ electrolyte was then densified through impregnating using yttrium and zirconium nitrate solutions followed by annealing treatment. The single cell assembled with the densified ScSZ presented an open circuit potential up to 1.004V at 600 °C and the maximum power density of 1356 mW cm -2 at 750 °C, 619 mW cm -2 at 650 °C, and 163 mW cm -2 at 550 °C. The performance of the cell was significantly improved by the post-spray densification treatment of the ScSZ electrolyte. The present result shows that the high performance NiO-YSZ/ScSZ/EWSB/LSCF cell at intermediate temperatures can be successfully fabricated by plasma spraying.
Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 347-355, May 4–6, 2022,
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Thermochemical processes are an appropriate way to improve the surface hardening of the material against wear. Thermal spraying is a group of deposition processes that can deposit different classes of materials. The use of thermomechanical process after metallic coatings deposition can result in a unique combination of bulk and surface properties. There are some studies that indicate the defects and stresses caused in the crystal lattice as one of the factors that most influence nitrogen diffusion during the nitriding process. The HVAF (High Velocity Air-Fuel) process can generate different fault conditions and stress-strain in the crystal lattice. The aim of this work is study the effect of the plasma nitriding or, as it is known, Glow Discharge (GD), on FeMnCrSiNi coating deposited with HVAF process. Initially, it was observed the formation of expanded austenite and CrN on the HVAF coating, followed by important increase on the hardness of the coating.
Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 422-431, May 4–6, 2022,
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High amorphous phase formation tendency, a desirable microstructure and phase composition and silicon evaporation are the challenges of spraying Yb 2 Si 2 O 7 environmental barrier coatings (EBCs). This research addresses these issues by depositing as-sprayed high crystalline Yb 2 Si 2 O 7 using atmospheric plasma spray (APS) without any auxiliary heat-treating during spraying, vacuum chamber, or subsequent furnace heat treatment, leading to considerable cost, time, and energy savings. Yb 2 Si 2 O 7 powder was sprayed on SiC substrates with three different plasma powers of (90, 72 and 53 kW) and exceptional high crystallinity levels of up to ~91% and deposition efficiency of up to 85% were achieved. The silicon mass evaporation during spraying was controlled with a short stand-ff distance of 50 mm, and an optimum fraction of Yb 2 SiO 5 secondary phases (<20 wt.%) was evenly distributed in the final deposits. The desirable microstructure, including a dense structure with uniform distribution of small porosities, was observed. The undesirable vertical crack formation and any interconnected discontinuities were prevented. Reducing the plasma power from 90 kW to 53 kW, while conducive for mitigating the silicon mass loss, was detrimental for microstructure by increasing the fraction of porosities and partially melted or unmelted fragments. The gradual decrease of the coating temperature after deposition alleviated microcracking but has an insignificant effect on the crystallinity level. Coatings annealed close to their operating temperature at 1300 °C for 24 hours demonstrated sintering and a crack healing effect, closing the tiny microcracks through the thickness. An improved coating composition was detected after annealing by the transformation of Yb 2 SiO 5 to Yb 2 Si 2 O 7 (up to ~10 wt.%).
Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 543-552, May 4–6, 2022,
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Iron-based coatings are often considered as replacement of hard chromium and WC-Co, as they pose lower health and environmental impact. In many cases the combination of mechanical and chemical properties of ferrous based alloys may be satisfactory and their relatively low cost make these coatings an interesting candidate for many applications. This study is inspired by opportunities to harden the ferrous base materials by strain hardening, solid solution strengthening, dispersion strengthening, and precipitation hardening. Already commercially available Fe-based coating materials with precipitates of mixed carbides and borides in the metastable austenitic matrix achieve a high hardness. In this study the cavitation erosion and abrasion resistance of various Fe-based coatings produced by HVAF and HVOF processes were investigated. Two experimental precipitation containing materials were prepared, and the sprayed coatings were tested for abrasive and cavitation erosion wear. In addition to precipitations, the importance of proportion of ferrite and retained austenite phases were studied by affecting the microstructure by heat treatments as the ability of different phases to affect hardening and ductility may become crucial in generating desired material properties. The properties of experimental and some commercial Fe-based alloys are compared with WC-Co and Cr 3 C 2 -NiCr coatings by property mapping.
Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 586-595, May 4–6, 2022,
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The health of railway material is of paramount importance for the safety of rail transportation. Railways are subject to heavy mechanical loading and to harsh environments, causing corrosion and damage that can bring to failure. The cold spray process has a great potential as an efficient and portable refurbishment technology, with the advantage of avoiding thermal effects on the substrate. In this study, a proof of concept for the cold spraying of railway steel onto a similar material is presented. This represents a first step towards the development of a cold spray solution for railway repair. First, the as-atomized steel powder revealed to be hardly sprayable. A heat treatment was then optimized and applied to the powder to induce microstructural evolution and to improve deposition efficiency and material quality. Therefore, the refurbishment of damaged railway samples by cold spray was proven to be viable. Finally, mechanical testing assessed the restoration of the structural properties needed for the application.
Proceedings Papers
ITSC 2022, Thermal Spray 2022: Proceedings from the International Thermal Spray Conference, 763-772, May 4–6, 2022,
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This study investigates the solid particle erosion performance of cold sprayed tungsten carbide-nickel coatings using alumina particles as erodent material. After coating fabrication, specimens were annealed in an electric furnace at a temperature of 600 °C for 1 hour. The coatings were examined in terms of microhardness and microstructure in the as-sprayed (AS) and annealed (AN) conditions. Subsequently, the erosion tests were carried out using a General Full Factorial Design with two control factors and two replicates for each experimental run. The effect of the annealing on the erosion behavior of the coating was investigated at the two levels (AS and AN conditions), along with the impact angle of the erodents at three levels (30°, 60°, 90°). Finally, two regression models that relate the impact angle to the mass loss were separately obtained for the two cold spray coatings.
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