Papers by Keyword: Flame Spray

Abstract: Lanthanum chromite (LaCrO₃) has been considered a promissing candidate for use as interconnect materials for solid oxide fuel cells (SOFCs), due to their excellent electrical properties. In this work, LaCr_1-xSn_xO₃ (x = 0 and 0.1) ceramic powders were prepared using the following synthesis routes: Flame spraying (FS) and microwave assisted combustion method (MCM). The powders were characterized by TGA, XRD and TEM. The TG curves showed weigh losses corresponding the dehydration of compounds as well as decomposition of secondary phases and organic matter. The XRD patterns indicated the formation of Sn doped LaCrO₃ phase by FS. The crystallite sizes of samples are in the range 20-36 nm. The TEM images revealed the presence of particles with spherical shape and uniform particle size distribution.

Abstract: Nozzle is one crucial part of rocket. In this research, the nozzle was made by AISI 4340 coated by termal barrier coating (TBC). The TBC material is Al₂O₃SiO₂ composite, with different variation: Al₂O₃ 20% SiO₂; 70% Al₂O₃ 30% SiO₂; and 60% Al₂O₃ 40% SiO_2. The aim of this research to observe the composittion which will produce optimum adhesive strength and the most widely formed mullite phase. Mullite is an expected phase formed from composite and it has thermal resistance during 1300°C. Coating process was conducted by flame spray with variation of plies. The effect ratio, plies, microstructure, phase, and adhesive strength of TBC were investigated using Scanning Electron Microscope (SEM), X-ray diffraction (XRD),) and adhesion testing. The results showed that the highest adhesive strength was 16 MPa for 20%SiO2 with 2 plies. The highest mullite forming was TBC. After heat treatment, it was found that the mullite phases were most widely formed at a composition of TBC 30% SiO₂-70% Al₂O₃.

Abstract: In this study, Al-12Si alloy coatings with different thickness were prepared through flame spray on the surface of the AZ91 magnesium alloy to improve its corrosion resistance. The corrosion resistance was characterized through corrosion potential using electrochemical methods. The Al-12Si alloy coatings were heat treated at 100 °C, 200 °C and 300 °C for 6, 12, 18 and 24 hours. The effects of heat treatment temperature and time on the coatings’ corrosion resistance were discussed. It was found that there were no phase changes during the deposition of Al-12Si coatings through flame spray and heat treatment. The greater the coating thickness was, the higher the corrosion potential was. After annealing, the inner microstructure of the Al-12Si coating was densified furtherly and the annealed coatings had higher corrosion potential and better corrosion resistance. The coating annealed at 100 °C for 18 hours had the highest corrosion potential and the best corrosion resistance in the same coating thickness.

Abstract: Partially amorphous iron-based coatings were produced onto aluminium using a powder flame-spraying process with a commercially available feedstock powder (Nanosteel SHS-7170) obtained from the Nanosteel Company Inc.. Several coating properties such as the microstructure, porosity, phase content, micro-hardness, and wear resistance were evaluated in the as-sprayed condition. As shown by the results obtained, the powder flame iron-based coatings perform relatively well in term of wear resistance in comparison with similar coatings produced using other expensive thermal spray techniques. Furthermore, this study shows that all the coating properties (microstructure, porosity, phase content, hardness and wear performance) depend strongly on the flame spraying parameters used. Finally, this paper demonstrates clearly that the flame-spray process may be used to produce amorphous iron-based coatings having a good wear resistance, and that this process appears to be a suitable inexpensive alternative to plasma or HVOF processes based on the present results.

Abstract: In order to improve the surface properties of the machine parts, the NiAl cladding Cr3C2 powder were flame and plasma sprayed. The morphology, microstructure, composition and wear properties of the coatings were examined. The results show that due to the exothermal reaction of the Ni and Al elements, the bonding strength of the coatings are improved, and the main compositions of the coatings are Ni3Al inter-metallic compound and Cr3C2. The flame sprayed and plasma sprayed coatings show almost the same micro-hardness and friction coefficient. But the microstructure of the plasma sprayed coating is more compact than that of the frame sprayed one and the wear resistance of the flame and sprayed coatings is 30% and 120% higher than that of the 1045 steel, respectively. The main wear mechanisms of the coatings are plastic deformation and spallation, and the high bonding strength and the uniformly distributed Cr3C2 particles play important anti-wear roles.

Abstract: In this study, microstructure and wear behavior of thermally sprayed Fe-based alloy coatings were investigated. Fe-based alloy coatings were formed on a carbon steel substrate and then heat-treated at temperature of 700 oC for 20 minutes. Dry sliding wear tests were performed using the sliding speeds of 0.4 and 0.8 m/s, the applied loads of 3 and 6 N. Microstructure and wear behavior of as-sprayed and heat-treated Fe-based amorphous coatings were studied using a scanning electron microscope(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD).

Abstract: SiC particulates reinforced Al matrix composites were fabricated by thermal spray process, and the dry sliding wear behavior against four different counterparts was investigated under a varying of the sliding speed and the applied load conditions. Al/SiC composites were fabricated by flame spraying, and the dry sliding wear tests were performed using the sliding speed of 0.4 m/s and 0.8 m/s at the applied load of 3 N. Sliding distance was kept at 1000 m for all the tests. Al2O3, ZrO2, Si3N4 and AISI 52100 balls were used as the counterparts. Wear tracks on the Al/SiC composites were investigated using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear behavior of Al/SiC composites was much influenced by counterpart materials.

Abstract: This study aims at investigating the effect of the sliding speed and the applied load on the dry sliding wear behavior of thermally sprayed Ni-based self-flux alloy coating. Ni-based self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then these coatings were heat-treated at temperature of 1000 oC. Dry sliding wear tests were performed using the sliding speeds of 0.2, 0.4, 0.6 and 0.8 m/s and the applied loads of 5, 10, 15 and 20 N. AISI 52100 ball (diameter 8 mm) was used as counterpart material. Wear behavior of Ni-based self-flux alloy coatings was studied using a scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that microstructure and wear behavior of the Ni-based self-flux alloy coatings were much influenced by the sliding speed and the applied load.

Abstract: Correlations between in-flight particle, splat and coating microstructure of thermally sprayed Ni20Cr were investigated. Flame spray and arc spray systems were employed for spraying Ni20Cr powder and Ni20Cr wire, respectively. The results showed that the arc spray process produced a broader size distribution for both in-flight particles and splats compared to flame process. Flower-like splat morphology was obtained from the arc spray whereas a pancake-like splat was obtained by flame spray. Ni20Cr coating sprayed by arc process had a denser microstructure, lower porosity and better adhesion at the interface. This could be due to the higher temperature and velocity from the arc spray process enhancing the melting and adhering for coating formation.