Iron Aluminide Coatings by Electrodeposition of Aluminum from an Organic Bath and Subsequent Annealing (original) (raw)
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Iron Aluminide Coating on Steel Surface by Mechanical Alloying at Elevated Temperature
Transactions of the Materials Research Society of Japan, 2009
A new type of iron aluminide coating on a steel substrate by mechanical alloying (MA) with Al-Fe powders was examined. Precoating was carried out by a high-energy planetary MA with Al-Fe powder at room temperature, followed by low-energy MA at an elevated temperature. In MA at 500 °C, the precoating layer becomes soft and the interdiffusion between Al and Fe is enhanced, resulting in the formation of a homogenous iron aluminide coating layer on a steel substrate. By MA at 500 ºC for 4 h, a Fe 2 Al 5 coating layer is formed for Al-25 at%Fe powder, and a FeAl coating layer with a small amount of Fe 2 Al 5 is formed for Al-50 at%Fe powder. The Fe-Al solid solution is achieved near the steel substrate/coating layer interface in a substrate, resulting in good bonding between the substrate and the coating layer. The Al-50 at%Fe coating layer has a hardness of 7.8 GPa and high fracture toughness.
Performance of Al-rich oxidation resistant coatings for Fe-base alloys
Materials and Corrosion, 2010
This multi-layer program has examined the oxidation resistance of Al-rich coatings made by chemical vapor deposition and pack cementation on ferritic-martensitic (e.g. T91, Fe-9Cr-1Mo) and austenitic (Type 304L, Fe-18Cr-8Ni) substrates at 650°-800°C. The main goal of this work was to demonstrate the potential benefits and problems with alumina-forming coatings. To evaluate their performance, oxidation exposures were conducted in a humid air environment where the uncoated substrates experience rapid oxidation, similar to steam. Exposure temperatures were increased to accelerate failure by oxidation and interdiffusion of Al into the substrate. The final results focused on thinner coatings with less Al and a ferritic Fe(Al) structure which have a lower thermal expansion than intermetallic phases. To improve the previously developed coating lifetime model, a final series of exposures were conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. For the coated Fe-(9-12)Cr specimens, there was little effect of Cr on lifetime at 800°C. At 700° and 800°C, thin coated austenitic specimens (304L and 316) continue to be protective at up to double the lifetime of a similar coating on T91. This increase could be attributed to the higher Cr content or the slower interdiffusion in austenitic substrates which is illustrated with electron microprobe measurements from thicker coatings stopped after 10-20 kh.
Journal of Coating Science and Technology, 2017
Iron aluminides (Fe3Al and FeAl3) coatings were fabricated on a steel substrate by selfpropagating high temperature synthesis (SHS) method. Raw materials, Fe and Al powders, were mixed at two different stoichiometry ratios (3:1 and 1:3). The mixtures and the substrate were placed in a furnace at 950 °C to ignite the SHS process. Coating phases were investigated using X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS). The microstructure of the coatings was analyzed with optical microscopy (OM) and scanning electron microscopy (SEM). The results confirmed that it is possible to produce Fe3Al and FeAl3 coatings on steel substrate using SHS method. In addition, the results show that the coatings were composed of two different phases and their microstructures were non-porous and dense. Wear resistance of the coatings were higher than that of the substrate.
Al-coated iron particles: Synthesis, characterization and improvement of oxidation resistance
Surface and Coatings Technology, 2008
A Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD) process has been successfully applied to coat Fe particles with Al. N 2 inert gas was used to transport the organometallic Al precursor (liquid triethylaluminium) inside the fluidized bed reactor whose temperature is 350°C. XPS analyses and TEM observations have revealed the presence of a thin alumina layer surrounding the Al coating. Oxidation treatments, performed in the temperature range 350-500°C, demonstrate that this multi-scale coating constitutes an efficient barrier to protect iron particles against oxidation. Such a treatment may be used to perform environmental barrier coatings around magnetic powders.
Preparation and oxidation of aluminum powders with surface alumina replaced by iron coating
Journal of Energetic Materials
Aluminum powders are well known for excellent release of energy during oxidation upon heating. However, this release of energy becomes limited due to formation of dense oxide (Al 2 O 3) layer on powder surface. In this study, reactivity of aluminum particles was improved by replacing oxide layer with metallic shell of iron using electroless plating technique. Three different bath compositions were selected for deposition of iron on aluminum particles. The surface morphology of prepared Al/ Fe core-shell composite powder was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Further, iron content in the composite powder was measured quantitatively using helium gas pycnometer while elemental analysis was performed by X-ray diffraction (XRD). Finally, thermo-physical behavior of the composite powder was investigated using simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC). The results showed that the synthesized Al/Fe core-shell composite powder exhibits higher energy release in comparison to the uncoated aluminum powder upon heating in air (up to 1180 °C). The powder with the densest iron coating released the highest energy.
Corrosion Perfomance of Fe-Al Intermetallic Coating in 1.0 M NaOH Solution
International journal of electrochemical science
Three different particle sizes were used to deposit FeAl and Fe 3 Al intermetallic coatings by thermal spray techniques: flame spraying and HVOF (High Velocity Oxygen Fuel). Coatings were characterized by SEM (scanning electron microscopy) and their characteristics are presented considering particle size and deposition process employed. Coatings performance was evaluated using electrochemical test in a solution of 1.0 M NaOH at room temperature. It was observed that deposition technique used and particle size influences the electrochemical performance of coatings. Coatings showed no significant variations in their current densities, but were one order of magnitude higher than those of base alloys, the corrosion potential of coatings were similar regardless of the particle size and more active than their alloy base.
Aqueous Corrosion Behavior of Iron aluminide Intermetallics
Journal of Materials Engineering and Performance, 2007
Iron aluminide intermetallics based on DO 3 ordered structure are being developed for use as structural materials and cladding material for conventional engineering alloys. Aqueous corrosion behavior of iron aluminides has been studied extensively by electrochemical techniques. Studies were carried out on pure Fe (99.9%), Fe-28Al (at.%), Fe-28Al-3Cr (at.%), and AISI SS 304 so as to compare and contrast their behavior in same experimental condition. Polarization behavior under different pH conditions was examined to evaluate their performance in acidic, basic, and neutral solutions. Pitting behavior was also studied in solution containing Cl-1 ions. The stability of the passive film formed was studied by current time transients and potential decay profiles. The presence of 3 at.% Cr in iron aluminides was found to improve the aqueous corrosion resistance and makes it comparable to AISI SS 304.
Intermetallics, 2020
In the present work, a novel technique has been introduced to obtain an aluminide coating by casting process and subsequent heat treatment. To do so, the aluminum sheet was placed at the bottom of a copper mold, then HH309 SS melt was poured into the mold. This technique was named Cast-Aluminizing (CA). The CA samples were heat-treated at the temperature range of 900-1050 � C for 0.5-5 h. The FE-SEM, XRD, and EDS were utilized to characterize the microstructure, phase analysis and chemical composition of cast-aluminized samples, respectively. Results showed that (Fe,Cr,Ni)Al 3 and (Fe,Cr,Ni) 2 Al 5 layers were formed at the Al/HH309 interface. FE-SEM analysis demonstrated a multi-layer aluminide coating on the heat-treated specimens. This coating consisted of (Fe,Cr,Ni) 2 Al 5 þ(Fe,Cr,Ni)Al 2 , (Fe,Cr,Ni)Al and α-Fe,Cr,Ni(Al) sub-layers. The growth kinetics investigation showed that the thickness of layers increased with the increase of the annealing temperature and time. The growth rate of layers obeyed a parabolic law. The activation energies for the growth of (Fe,Cr, Ni) 2 Al 5 þ(Fe,Cr,Ni)Al 2 , (Fe,Cr,Ni)Al and α-Fe,Cr,Ni(Al) layers were about 203, 250 and 247 kJ/mol, respectively. Microhardness measurements revealed that (Fe,Cr,Ni) 2 Al 5 þ(Fe,Cr,Ni)Al 2 , (Fe,Cr,Ni)Al and α-Fe,Cr,Ni(Al) layers had a hardness of about 820-1040, 580-710 and 380-470 HV, respectively. The resistance to oxidation of castaluminized and heat-treated (CA þ HT) samples in the air at 1000 � C was studied. The CA þ HT samples exhibited higher oxidation resistance than uncoated samples due to the formation of a protective Al 2 O 3 layer on the surface.
Mechanical Alloying-assisted Coating of Fe–Al Powders on Steel Substrate
Makara Journal of Technology, 2020
The coating layer of Fe-Al powders on the steel substrate was prepared by mechanical alloying at room temperature. Fe, Al, and the steel substrates were milled with high-energy ball milling for 32 h with a ball-to-powder ratio of 8 in an argon atmosphere to prevent oxidation during milling. Although mechanical alloying was performed for 32 h, no new phases were observed after mechanical alloying, as analyzed by X-ray diffraction. However, the crystallite size of the milled powders for 32 h decreased by factor two compared with the initial powders. Scanning electron micrographs showed that the coating layers formed >8 h after mechanical alloying. The intermetallic Fe 3 Al formed after the substrate was annealed at 500 ℃.
MATERIALS SCIENCE-POLAND
The paper presents results of studies of structure and properties of the NiAl + FeAl type diffusion layers fabricated on 316L steel (00H17N14M2) by the chemical vapour deposition using aluminium chloride (AlCl 3) in a hydrogen atmosphere as a carrier gas. The layers were examined using light and scanning electron microscopy. Chemical composition analyses were carried out by EDS and phase content was investigated by XRD. Corrosion resistance was tested using the potentiodynamic method in 0.5 M NaCl, and layer/structure adhesion was tested by the scratch test. The results obtained indicate that the 50 μm thick layers fabricated on the 316L steel substrate show very good adhesion combined with very good corrosion resistance.