Kinetics of the High Temperature Oxidation of the Inconel 686 Coatings in the Waste Incineration Ash (original) (raw)
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High-Temperature Corrosion of Ni-Base Alloys by Waste Incineration Ashes
Acta Physica Polonica A, 2016
Ni-Cr-Mo alloys, e.g. Inconel 625 and 686, exhibit high-temperature corrosion, oxidation and wear resistance. For this reason, these alloys are typically used as a coating material in different environments as effective solid-state diffusion barriers between the corrosive atmosphere and the base metal. To perform the Ni-base weld overlays, without introducing too much Fe, a new welding technique called cold metal transfer was used. High-temperature corrosion of boiler parts during incineration of waste was investigated. Boiler tubes were coated with Inconel 625 and Inconel 686 nickel alloys and, after subjecting them to waste incineration ashes, they were examined by scanning electron microscopy with energy dispersive X-ray spectrometer to reveal different corrosion mechanisms and their causes. Results indicate a strong dependence of the boiler steel corrosion on anions in the incineration waste ash. X-ray diffraction characteristics of the scale showed that surface corrosion processes induce the formation of CrO2, NiO. The presence of iron in the clad weld surface is conductive to the formation of the Fe2O3 oxide.
Influence of the Oxygen Partial Pressure on the Oxidation of Inconel 617 Alloy at High Temperature
Oxidation of Metals, 2010
Ni-based superalloy Inconel 617 (IN617) is one of the main candidate structural materials for high temperature components (heat exchanger) of the gascooled fast reactor (GFR), a possible candidate for generation IV nuclear reactor. The material in operating conditions will be exposed to impure He at a temperature of around 850°C. The impurities are expected to be oxidizing (such as O 2 , H 2 O) but since no feedback experience is available for this type of reactor, the level of impurities is completely unknown. Hence, an attempt has been made to understand the influence of oxygen partial pressure on oxide composition and on the oxidation mechanisms of IN617 at 850°C. To achieve this, oxidation tests were performed at 3 different range of partial pressure: 10-5 , 0.2 and 200 mbar. Tests were performed from 1 h to 28 days and the obtained oxide layers were characterized using MEB, EDX, XPS, XRD and GD-OES. The oxide layers were mainly composed of chromia containing TiO 2 and thickening with time. Aluminium oxide formed internally. Other oxides were detected in the scale, such as NiO, CoO, MoO 3 and MnO 2 , except for the lowest oxygen partial pressure experiments, where a selective oxidation took place. The scale-growth mechanism was cationic for low and medium oxygen partial pressure conditions. A growth following a transient oxidation mechanism was observed for high oxygen partial pressure.
Applied Surface Science, 2013
In order to understand the influence of humidity on high temperature oxidation of Inconel 600 alloy, in this work, water vapour (absolute humidity varying from 0% to 19%) was introduced in the thermal gravimetric analysis (TGA) system under artificial air between 600 • C and 900 • C. The oxides identification and the residual stress in the oxide layers have been studied by X-ray diffraction method in each of two oxide phases, simultaneously. The oxide surface morphology, cross-section microstructure and the chemical composition of the oxide layers were determined by FEG-SEM (Field Emission Gun Scanning Electron Microscope) observation and FEG-SEM EDS (Energy-dispersive X-ray spectroscopy) analysis. Depending on the oxidation temperature, the humidity and the oxidation duration, the oxide layer differed significantly. The residual stress levels in the different oxide layers (NiO-type layer and Cr 2 O 3-type layer) have also been affected by the introduction of the water vapour. According to the analysis results, the residual stresses on oxide mainly came from the growth stress and thermomechanical stress; and the oxide growth stress was especially affected by humidity at high temperature.
Samples of Inconel 600 were isothermally oxidized in a controlled atmosphere with a special mounting at high-temperature oxidation. Along with this experimental study, a simulation of thermodynamic behavior of the material in the same oxidation conditions was carried out using the Thermo-Calc code. The thermodynamic modeling is able to predict the phase nature and its distribution in the structure of the surface layer resulting from the corrosion of the material in thermodynamic equilibrium in the absence of mechanical stress. The results of this simulation are supplemented to results obtained from the analysis by glow discharge spectrometry (GDS) which is performed on the samples tested.
A two-step pack cementation technique was used to cover nickel-based IN-738LC superalloy with a Cr-aluminide coating layer. The IN-738LC/Cr-aluminide samples were oxidized at 900°C for 350 and 700 h, isothermally, and 175 and 350 h, cyclically. Each cycle lasted for 25 h. Effects of the isothermal and the cyclic oxidation on (a) morphology, (b) new-phase formation, (c) weight gain, and (d) oxidation reactions were investigated by scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction, and weight gain measurements. From results, it was concluded that the oxygen attack was more severe during the cyclic oxidation than the isothermal procedure. Kinetics of the reactions indicated a & S. K.
Corrosion Science, 2020
The microstructure and oxidation resistance of Laser Beam Melted (LBM) and Conventionally Manufactured (CM) Inconel 625 alloys were studied at 900°C and 1050°C. The microstructure of the LBM samples was cellular, with Nb and Mo segregations located at the cell walls. At 900°C, the oxidation rate was similar for both materials but was clearly higher for the LBM material at 1050°C. This high oxidation rate induced poor oxide scale compactness, void formation in the subsurface region and the formation of a high amount of Nb 1.5 Cr 0.5 O 4 at the alloy-oxide interface.
Chinese Journal of Aeronautics, 2007
IN 600 alloy was coated with two different types of coatings, Cr-modified aluminide coating this is called (Aluminizing-Chromizing) and Y-doped chromium modified aluminide coating this is called (Aluminizing-Chromizing-Yttriumizing). Diffusion coating was carried at 1 050 ℃ for 8 h under Ar atmosphere by simultaneous aluminizing-chromizing process and by simultaneous aluminizing-chromizing-yttriumizing. Cyclic oxidation tests were conducted on the uncoated and on the coated IN 600 alloy in the temperature range 800-1 000 ℃ in CO 2 for 100 h at 10 h cycle.The results showed that the oxidation kinetics for uncoated Inconel 600 alloy in CO 2 is parabolic and the phases present are NiO, (Fe, Cr) 2 O 3 , NiFe 2 O 4 and NiCrO 4. The oxidation kinetics for both coated systems in CO 2 was found to be parabolic and the value of k P for both coated systems were found to be lower than that for uncoated IN 600 alloy. Oxide phases that formed on coated systems are Al 2 O 3 and NiCrO 4. The role of yttrium can be attributed to its ability to improve the adherence of the oxide scale.
In this study, high temperature reactions of Fe-Cr alloys at 500 and 600°C were investigated using an atmosphere of N 2 -O 2 8 vol% with 220 vppm HCl, 360 vppm H 2 O and 200 vppm SO 2 ; moreover the following aggressive salts were placed in the inlet: KCl and ZnCl 2 . The salts were placed in the inlet to promote corrosion and increase the chemical reaction. These salts were applied to the alloys via discontinuous exposures. The corrosion products were characterized using thermo-gravimetric analysis, scanning electron microscopy and X-ray diffraction.The species identified in the corrosion products were: Cr 2 O 3 , Cr 2 O (Fe 0.6 Cr 0.4 ) 2 O 3 , K 2 CrO 4 , (Cr, Fe) 2 O 3 , Fe-Cr, KCl, ZnCl 2 , FeOOH, r-FeCrMo and Fe 2 O 3 . The presence of Mo, Al and Si was not significant and there was no evidence of chemical reaction of these elements. The most active elements were the Fe and Cr in the metal base. The Cr presence was beneficial against corrosion; this element decelerated the corrosion process due to the formation of protective oxide scales over the surfaces exposed at 500°C and even more notable at 600°C; as it was observed in the thermo-gravimetric analysis increasing mass loss. The steel with the best performance was alloy Fe9Cr3AlSi3Mo, due to the effect of the protective oxides inclusive in presence of the aggressive salts.
Coatings
As it increases the pressure and temperature of incoming steam and decreases CO2 emissions, oxidation is crucial for materials used in power plants to increase their efficiency. Compound composite (Cr2O3 + YSZ) coatings applied to Inconel 718 (EN8) substrates using the Atmosphere Plasma Spray technique are anticipated to increase structural resistance when subjected to high pressure and temperature oxidation conditions of service. The nickel-based superalloys EN8 and EN8/Yttria (8% Y2O3) Stabilized Zirconia (YSZ)/Cr2O3 were subjected to high-temperature oxidation tests in the open air at 1050 °C for approximately 12, 24, 48, and 100 h. EN8 is not appropriate for prolonged use at 1050 °C as can be seen from scanned electron microscope and energy dispersive X-ray spectroscopy analyses on isothermally oxidized samples. The findings demonstrated that the EN8 alloy exhibited more significant weight variations over 48 h at high temperatures because its chromia oxide scale was continuously...
Surface & Coatings Technology, 2017
The power generation industry has been progressively shifting towards higher operating steam temperatures and pressures to increase efficiency and reduce CO 2 emissions. However, higher operating temperatures lead to more aggressive oxidation of the boiler components. A promising route to improve the durability of degradation-prone components is through deployment of high-performance coatings. In the present work, four Ni-based coatings-Ni21Cr, Ni5Al, Ni21Cr9Mo, and Ni21Cr7Al1Y-thermally sprayed by the high-velocity air fuel (HVAF) technique on boiler steel (16Mo3) substrates were investigated. The isothermal oxidation behavior of the coatings was studied in ambient air environment at 600°C for different time intervals i.e. 1, 5, 10, 24, 48, 96, and 168 h. The oxidation behavior of the as-sprayed and polished coatings was compared. The protective α-Al 2 O 3 was not detected on the exposed alumina-forming NiAl coating. On the other hand, Cr 2 O 3 along with a small amount of NiO were the main oxidation products on the surface of the NiCr and NiCrMo coatings, and were found to be relatively less protective. The mixed-oxide scale forming NiCrAlY coatings showed the best oxidation resistance due to the formation of a thin and slow-growing Al 2 O 3 scale along with Ni(Al,Cr) 2 O 4 and Cr 2 O 3. The polished coatings were found to significantly reduce the oxidation rate in each case as the protective scaleforming elements were more uniformly supplied to the surface oxide scale by removing the surface asperities.