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Thermal spraying is a group of processes in which finely divided metallic or nonmetallic surfacing materials are deposited in a molten or semi-molten condition on a prepared substrate to form a spray deposit. The surfacing material may be in the form of powder, rod, cord, or wire, and the different spraying processes are generally categorized into...
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... vortex plasma torches using a button-type cathode and high gas flow rates have been developed to spray relatively large quantities of pow- der (up to 20 kg/h to 25 kg/h). Figure 7 shows a schematic diagram of such a plasma torch (34). The nozzle internal diameter is about 8 mm, and typical working conditions are 200 slm to 300 slm N 2 , 100 slm to 150 slm H 2 , 500 A, and 400 V. ...
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This paper describes the equipment design of E. O. Paton Electric Welding Institute and technology of microplasma spraying of coatings from powder and wire materials for applying biocompatible coatings for medical implants. The given equipment was introduced at an experimental robotics complex for microplasma spraying at D. Serikbayev East-Kazakhst...
Citations
... Structure of a plasma-sprayed deposit (reprinted from Ref.[21]). ...
This work explores the advantages and disadvantages of a methodology using high-energy X-ray diffraction to determine residual stresses in multilayer structures produced by atmospheric plasma spraying. These structures comprise a titanium alloy substrate (Ti64), a bonding layer (Ni-Al), and an abrasive coating (Al2O3). This study focuses on analyzing the residual stress gradients within these layers. The presented method is used to determine stresses across the entire thickness of multilayer structures. Experiments were carried out using a high-energy rectangular beam, operating in transmission mode, on the cross-section of the sample. The results indicate variable stresses throughout the depth of the sample, particularly near the layer interfaces. The semi-automatic methodology presented here enables us to follow stress evolution within the different layers, providing indications of the load transfer between them and at their interfaces. The sin2ψ method was used to analyze the diffraction data and to determine the stresses in each phase along the sample depth. However, interpreting results near the interfaces is complex due to the geometric and chemical effects. We present a discussion of the main advantages and disadvantages of the methodology for this kind of industrial sample.
... Cold spray (CS) and Warm spray/High-Velocity Air Fuel (HVAF) have been introduced as solutions that overcome oxidation and provide coatings with improved properties [3]. CS is a solid-state deposition process that generates coatings, via the supersonic spraying of powder feedstock material, that will deposit under high levels of plastic deformation [3]. ...
... Cold spray (CS) and Warm spray/High-Velocity Air Fuel (HVAF) have been introduced as solutions that overcome oxidation and provide coatings with improved properties [3]. CS is a solid-state deposition process that generates coatings, via the supersonic spraying of powder feedstock material, that will deposit under high levels of plastic deformation [3]. In this process the shrinkage range is low, leading to a lower level of residual stresses and making it possible to apply thicker deposits. ...
... In HPCS, helium is frequently used since it is a lighter gas, making it possible to go to higher velocities during spraying [9]. As a result, more particle plastic deformation may occur, and a porous-free (dense) coating structure may be produced leading improved mechanical properties [3]. But, due to the high cost of helium as a non-renewable source, nitrogen or compressed air are preferred to use in CS [4]- [6], [10]. ...
As a supersonic solid-state deposition process, Cold Spray (CS) has a unique role among other thermal spray techniques as it uses compressed and heated gas to accelerate particles to a critical velocity. CS can be an expensive process, especially when helium is used as a processing gas. In recent thermal spray developments, High-Velocity Air Fuel (HVAF) has taken a specific place in terms of providing dense and strong coatings similar to CS, but also coatings with less oxidation than High- Velocity Oxy-Fuel (HVOF). In contrast to these techniques, HVAF uses a mixture of fuel and air, instead of pure oxygen as in HVOF, to accelerate particles. Therefore, HVAF appears as a relatively cheaper and environmentally friendly alternative for the deposition of a wide variety of materials. The aim of this research is to produce fully dense copper coatings with limited oxidation using an inner diameter (ID) HVAF system and to compare the microstructure with CS copper coatings. Coating microstructures, surface roughness, and microhardness are studied using different characterization methods such as Scanning Electron Microscopy (SEM). Through this paper, the influence of both spray processes, CS and ID-HVAF, on the deposition of copper coatings is discussed. Cross-sectional studies of different coatings show a fairly dense microstructure for CS and ID-HVAF coatings. Moreover, it is discussed how the copper coating properties can change upon modifying the spray parameters.
... All deposited Al 2 O 3 coatings demonstrated good adhesion to the steel substrate. There is a minimal number of microcracks and pores between the substrate and the coating; however, over the entire coating width, there are a lot more cavities, which are common for plasma-sprayed coatings [30,31]. The coating thickness was similar for all samples (around 40 µm). ...
... All deposited Al2O3 coatings demonstrated good adhesion to the steel substrate. There is a minimal number of microcracks and pores between the substrate and the coating; however, over the entire coating width, there are a lot more cavities, which are common for plasma-sprayed coatings [30,31]. The coating thickness was similar for all samples (around 40 μm). ...
In this study, alumina coatings were formed using atmospheric plasma spraying, increasing the torch power from 29.4 to 45.1 kW. The surface morphology of the coatings was determined using scanning electron microscopy; the elemental composition was examined using energy-dispersive X-ray spectroscopy (EDS); phase composition was investigated using X-ray diffraction; and surface roughness was determined using a profilometer. The steel surface temperature was measured using a type-K thermocouple, and the plasma jet temperature, at a distance of 70 mm, using a type-B thermocouple. Alumina particle velocity was calculated by analyzing high-speed camera footage using ImageJ software. The results indicate that plasma jet temperature, speed, and in-flight particle velocity increased with plasma torch power. Furthermore, the amount of γ-Al2O3 phase in the coating increased, and the α-Al2O3 decreased with increasing plasma power. The surface roughness (Rq) of the Al2O3 coatings decreased from 7.13 to 5.54 μm, with an increase in torch power. The EDS measurements indicate that the increase in torch power did not affect the elemental composition of as-sprayed coatings. The results provide a wider understanding of an atmospheric plasma spray technique, optimizing and controlling the parameters using air as a primary gas.
