This study examines the influence of NiCrAlY powder with and without Al2O3 Reinforcement doses of 5, 10 and 20% by weight, produced by plasma spraying method have been investigated. In order to prepare a composite powder, shaft ball mill blender for an hour for each pow More
This study examines the influence of NiCrAlY powder with and without Al2O3 Reinforcement doses of 5, 10 and 20% by weight, produced by plasma spraying method have been investigated. In order to prepare a composite powder, shaft ball mill blender for an hour for each powder were used. The NiCrAlY powder and powder composite NiCrAlY / Al2O3 with values of 5%, 10%, 20% Al2O3 were coated on Inconel 718 substrates by plasma thermal spraying. In order to evaluate the microstructure, morphological and thermal stability evolutions of the powders and coatings were investigated using X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy and optical microscopy. Vickers micro and macro hardness test was used to evaluate the hardness..The pin-on -disk test with 5 N was used to cold resistance assessment of coatings. Findings showed that the composite coatings NiCrAlY/Al2O3 because of the size and morphology of different ingredients, has a higher porosity, but in terms of mechanical properties due to reinforced phase, improvements in composite coatings were observed. Evaluate the wear behavior of Al2O3 10% coatings showed that 37.7× 10-6(mm3/Nm)abrasion resistance better than other coatings, especially coatings from powders without reinforcement 114.6× 10-6 (mm3/Nm) abrasion resistance had.
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In this research, NiCrAlY powder was applied on steel, and Hastelloy X substrates with solid shielding shrouded plasma spray (SSPS) process and compared with atmospheric plasma spraying (APS). The high-temperature oxidation test was also performed on the coatings, and t More
In this research, NiCrAlY powder was applied on steel, and Hastelloy X substrates with solid shielding shrouded plasma spray (SSPS) process and compared with atmospheric plasma spraying (APS). The high-temperature oxidation test was also performed on the coatings, and the microstructure of coatings was studied by optical microscopy (OM) and scanning electron microscopy (SEM). To investigate the influence of the SSPS process on the properties of metallic coatings, variable parameters; such as type of shroud gas (Ar, H2), the gas injection method (internal, external or simultaneous) and the flow rate of that, were examined. During the use of shroud gas, the temperature of the plasma jet has increased significantly. The oxidation test results showed the proper performance of NiCrAlY coating under the protection of argon internal shroud gas with a flow rate of 75SLPM, which was able to perform the best plasma flame protection during spraying. It can lead to a reduction in oxide and porosity of coating up to 8%. Also, the lowest thermally grown oxide (TGO) thickness was obtained for this sample after 200 hours of oxidation, indicating its excellent performance in maintaining the Al for the formation of the continuous α-Al2O3 layer during high-temperature oxidation.
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In this research, the properties of the coating applied by conventional plasma spray and with inert gas shroud has been studied and compared, in the way that nozzle like part attached to plasma gun in order to protect the plasma jet by exiting nitrogen from the nozzle. More
In this research, the properties of the coating applied by conventional plasma spray and with inert gas shroud has been studied and compared, in the way that nozzle like part attached to plasma gun in order to protect the plasma jet by exiting nitrogen from the nozzle. The Microstructural characterization of the coatings was performed by optical microscope and scanning electron microscope equipped with energy dispersive spectroscope. Hardness of coatings is also measured by Vickers method under the applied load of 30 gram-force. Isothermal oxidation and thermal shock tests are done at 1000 and 950ºC respectively. Post-spray results show that the use of nitrogen gas shroud is useful and coating achieved by nitrogen shroud has less oxide and porosity and has more homogeneous structure. Results from isothermal oxidation show that TGO layer growth rate in the specimen sprayed by nitrogen shroud is less. Thermal shock test shows that the specimen sprayed by nitrogen shroud has more resistance against thermal shock due to layer by layer and regular growth of TGO and having less oxide and porosity in comparison with the same specimen sprayed without nitrogen shroud. Also, the microhardness of sprayed coating without nitrogen shroud was 35 Vikers more than the applied coating with nitrogen shroud.
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In this research, CoNiCrAlY powder was deposited by high-velocity oxy-fuel (HVOF) and low-pressure plasma spraying (LPPS) processes on IN738 nickel-based superalloy substrates. The high-temperature oxidation test was performed on the coatings at a temperature of 1050 ̊C More
In this research, CoNiCrAlY powder was deposited by high-velocity oxy-fuel (HVOF) and low-pressure plasma spraying (LPPS) processes on IN738 nickel-based superalloy substrates. The high-temperature oxidation test was performed on the coatings at a temperature of 1050 ̊C and a time of 200 hours in a muffle furnace. The microstructure and phase composition of the coatings were investigated by SEM and XRD before and after the oxidation test. The porosity (volume percentage) and surface roughness (micrometer) were measured for HVOF coating as 0.6 and 4.4, and for LPPS coating as 2 and 6.62, respectively. The HVOF coating consisted of γ-CoNiCr and β-(Co,Ni)Al, while the LPPS coating included a single phase γ-CoNiCr. The disappearance of the β phase in the LPPS coating after spraying was due to dissolution in the plasma jet and its non-recovery in the conditions of rapid quenching and non-equilibrium solidification. This phase was recovered after heat treatment. The microstructure of the LPPS coating had much less oxide than the HVOF coating due to depositing at low oxygen pressure in the vacuum chamber. After 200 hours of oxidation test, the amount of β phase (as an oxidation resistance criterion) was completely consumed in the LPPS coating, while the HVOF coating contained the retained β deposits. The average thickness of TGO layer for HVOF and LPPS coatings was 5.2 and 7.1 μm, respectively. The dispersed oxides in the microstructure, lower roughness and denser structure of HVOF coating were reasons for the higher oxidation resistance of HVOF coating than LPPS.
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