Sulfidation Resistance Research Articles

High temperature oxidation of Fe-Cr alloys in atmospheres containing 2.0 % SO2 + 5.0 % O2

In this study, we examined the microstructure and composition of the scales formed after exposures from 825 °C through to 950 °C for 60 min in the atmosphere containing 2.0 % SO2 + 5.0 % O2 gas. The scale composition after oxidation mainly depends on temperature but not on the Cr content. The FeS formation temperature was 915 ℃, while its melting temperature was 925 ℃. Two mechanisms of the FeS formation are proposed. The eutectic transformation of molten FeS occurred during the subsequent cooling process, resulting in lamellar FeS + Fe-S-O compounds. The study indicated that Cr exhibits oxidation but not sulfidation resistance.

Slow-Growing Titanium Dioxide on Ti-48Al Porous Alloy Mediated by Nb and Cr Addition: Perspective via Local Metal–Oxygen Bonding Strength

TiAl porous alloys exhibit potential for application in high-temperature flue gas filtration, because of their satisfactory mechanical properties and excellent high-temperature creep resistance. However, poor oxidation resistance and corrosion resistance at temperatures exceeding 800 °C considerably limit the practical applications of TiAl porous alloys. The disadvantages of TiAl alloys can be mitigated by adding a specific amount of alloying elements to delay oxygen diffusion. In this study, two kinds of porous alloys, Ti-48Al and Ti-48Al-2Nb-2Cr, are used to evaluate the high-temperature oxidation resistance and sulfidation resistance of TiAl-based porous alloys. With the addition of alloying elements Nb and Cr, the high-temperature oxidation resistance and sulfidation resistance of the TiAl alloys have greatly improved. The mechanisms underlying phase transformation are also explained using the first-principles theory. The excellent antioxidation and anti-sulfidation properties of the Ti-48Al-2Nb-2Cr porous alloy are mainly attributed to the markedly reduced free energy of Al2O3 formation and suppress the presence of TiO2 at elevated temperatures, as explained by first-principles calculations. The Ti-48Al-2Nb-2Cr porous alloy has advanced the application of multiple alloying in high-temperature flue gas filtration.

Metal–Organic Framework Coating for the Preservation of Silver Nanowire Surface‐Enhanced Raman Scattering Platform

AbstractAg nanostructures are investigated as efficient plasmonic platforms because of their superior optical properties. However, the easy corrosion of Ag surfaces by reaction with oxygen or sulfur in the atmosphere can seriously affect the optical properties of Ag nanostructures, limiting the stable operation of Ag platforms. Herein, it is reported that a metal–organic framework (MOF) enables an Ag nanowire (NW) surface‐enhanced Raman scattering (SERS) platform to be corrosion resistant. A single Ag NW on a film (Ag‐NOF), an effective SERS‐active platform, is coated with the zeolitic imidazolate framework‐8, and then the corrosion resistance of the Ag‐NOF structures is examined under a variety of harsh environmental conditions. Interestingly, the MOF‐coated Ag‐NOF platforms are found to provide excellent oxidation and sulfidation resistance. With the MOF coating, the SERS signals of the Ag‐NOF structures are well maintained under harsh conditions, while the signals are reduced without MOF coating. More importantly, it is clearly verified that the MOF coating preserves the DNA sensing performance of the Ag‐NOF platform even after storage under several environmental conditions. Based on the results, it is anticipated that these MOF‐coated Ag‐NOF structures will be used as long‐term stable SERS sensors for the detection of biological and chemical molecules.

High-temperature Sulfidation and Oxidation Behavior of Plasma-sprayed Al-Mo Coatings

Gas burner is the key component of coal-water slurry gasifier system. However, due to the sulfidation at high temperature, gas burner often fails in advance, which affects the stable operation of the system. In this work, Al-Mo coatings were deposited by plasma spraying with a Mo bonding layer. The sulfidation and oxidation behavior of the Al-Mo coatings was studied and compared with those of Mo coatings and Inconel 600 alloy at 973, 1073 and 1173 K. Results show that both the high-temperature sulfidation resistance and the high-temperature oxidation resistance of Al-Mo coatings are superior to those of Mo coatings. The high temperature sulfidation resistance of coatings is better than that of Inconel 600 alloy. Plasma-sprayed Al-Mo coatings with a Mo bonding layer are promising candidates for the corrosion protection of steels in a sulfur/oxide-rich atmosphere.

Sulfidation Resistance of Porous FeCrAl Alloy

FeCrAl alloy is regarded as the optimization material for coal-gasification purification with high temperature, due to its good mechanical property, oxidation resistance and sulfide resistance. This paper focuses on the effect of preoxidation on sulfidation resistance of porous FeCrAl alloy. The continuous and dense Al2O3 film, which was formed on the surface of porous FeCrAl alloy after preoxidation, can prevent the diffusions of atom S and metal ion and improve the sulfidation resistance.

Investigation of oxidation behavior of synthesized Fe2Al5 and FeAl

Recently, Iron aluminide compounds have attracted considerable interest due to their attractive physical and mechanical properties such as high-temperature applications, good oxidation and sulfidation resistance, low density and low production cost. In the present research, the following methodology was undertaken: first, FeAl and Fe2Al5 were synthesized. Then the Fe2Al5 and FeAl oxidation behavior was investigated in the air for 2–60 h at 850 °C. It was found that FeAl is more resistant to the oxidation compared to Fe2Al5. The FeAl oxidation rate reaches a plateau in higher temperatures while Fe2Al5 oxidation curve has an upward trend with the fluctuation. The reason for such a behavior is the difference in alumina growth mechanism.

Design of anti-tarnish sterling silver Ag-Cu-Zn alloy and investigation of silicon addition influence on mechanical and corrosion characteristics

This paper presents investigations of the influence of silicon addition on the mechanical and corrosion characteristics of the sterling silver Ag-Cu-Zn alloys. The procedure for obtaining Ag-Cu-Zn-Si alloys in small ranges of composition was also presented. Vickers hardness tests and three electrochemical tests were performed on the samples in this study. Open circuit potential measurements, linear polarization resistance method, and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in 0.9% NaCl solution, artificial sweat, 0.1 and 0.01 M sodium sulfide solutions. It was shown that addition of silicone increases hardness and generally improves sulfidation resistance and corrosion characteristics in near-neutral chloride solutions of the Ag-Cu-Zn alloys.

High-Temperature Corrosion of Incoloy Alloy 800 in N<sub>2</sub>/H<sub>2</sub>S Gas

The nickel-iron-chromium-based alloy, Incoloy alloy 800, was corroded at 600, 700 and 800 °C for 10-70 h under 1 atm of total pressure in three different atmospheres, viz., 1 atm of N2, N2/H2O, and N2/H2O/H2S-mixed gases. The corrosion rates always increased with addition of H2O and, much more seriously, with the addition of H2S gas. In N2 and N2/H2O gases, oxidation prevailed. In N2/H2O/H2S gases, sulfidation dominated. The corrosion resistance increased in the T22 steel displayed better resistance to oxidation and sulfidation than Fe-2Mn-0.5Si steel, owing to the presence of Cr. Strong enrichment of Cr and the presence of Ni and Fe were noticeable in the inner scale. Chromium sulfidized to FeCr2S4 in N2/H2O/H2S gases, which was responsible for the enhanced sulfidation resistance of T22 compared with Fe-2.0Mn-0.5Si steel.

Synthesis <i>In Situ</i> Composite TiAl-Based with Particulate Al<sub>2</sub>O<sub>3</sub> Reinforcement by Powder Metallurgy Route

A major effort has been made over last 20 or so years to introduce TiAl-based alloys into the market-place as engineering component. Recently, titanium aluminide based composites are competitive candidate for aerospace use due to the favorable properties of matrix material, such as low density, high specific strength and relative good properties at elevate temperature [1-4]. The amount of aluminum in titanium alloys exceeds that used in conventional alloys and can range from 10 to 48at%. This concentration of aluminum allows the formation of anin-situalumina reinforcement which is responsible for the excellent oxidation, sulfidation and carburization resistance at temperatures of 1000°C and higher. However, their brittleness and rapid crack growth rate at low to intermediate temperature hinders their application/3/. Nevertheless, nanostructure of monolithic TiAl is unstable at elevate temperatures which deteriorate the high temperature properties. In order to improve the high temperature strength of intermetallic, ceramic particles can be utilized as reinforcements [4, 5]. Recently, in-situ techniques have been utilized to fabricate TiAl-Al2O3composite through displacement reaction between TiO2and Al in planetary ball milling and subsequence heat treatment. The knowledge of reaction characteristic in the Al-TiO2system is great importance to optimize the processing/4, 6/. The chemical compatibility with the iron aluminide matrix at temperature above 1000°C is an important factor for the selection of reinforcements because extreme interfacial reaction during processing results in the degradation of mechanical properties [3, 4].

Evaluation of Sulfidation Resistance of Atomized Fe40Al Based Intermetallics

ABSTRACTThe isothermal oxidation-sulfidation of Fe-40Al based intermetallics alloys in N2/SO2 gas mixture at 625, 700 and 775°C were evaluated. Fe40Al, Fe40Al+0.1B, Fe40Al+0.1B+10Al2O3 alloys were produced by atomization and deposition. Isothermal gas exposition was reached during 48 hours. FeAl based alloys showed good sulfidation resistance, presenting both small weight gain and weight change fluctuations. At 625°C, the Fe40Al+0.1B alloy had the biggest weight gain; on the other hand the Fe40Al alloy exhibited the biggest sulfidation resistance. At 700 and 775°C, the Fe40Al+0.1B alloy presented the smallest weight gain, however Fe40Al alloy presented higher weight gain, that is to say, the smallest sulfidation resistance at those temperatures. The variation in the weight gain curves were discussed in terms of formation and detachment of sulfides, and by local attack on the alloy surface as the temperature increasing. The results are supplemented with characterization by SEM and analysis of X-rays dispersion.

Multilayer coatings for corrosion protection of coal gasifier components

Deposition of TiAlN/Nb, TiAlN/Ta, TiAlN/W and TiAlN/Zr multilayer coatings on 409 stainless steel was studied by CVD in a fluidized bed reactor (FBR-CVD). The coatings consisted of four TiAlN layers with individual thickness of 2.5–3.5 μm, and four metal interlayers with thicknesses in the range of 100–250 nm. The W interlayers suffered partial nitridation during the coating process and the resulting coatings had poor adhesion. Deposition of Zr through reduction of ZrI 4 by H 2 was found to be inefficient. Both TiAlN/Nb and TiAlN/Ta coatings showed good adhesion, but only TiAlN/Nb provided sulfidation resistance to 409 steel during exposure to simulated coal gas at 1173 K for 300 h. Though outward diffusion of Cr took place during the corrosion test, the results reported in this paper suggest that TiAlN/Nb coatings are promising candidates for corrosion protection of steels under typical coal gasifier conditions.

Sulfidation resistance of CeO2-modified HVOF sprayed FeAl coatings at 700 °C

FeAl based coatings containing various amounts of CeO2 ranging from 0 to 8 wt.% CeO2 were deposited onto carbon steel by high-velocity oxygen fuel spraying, and were tested at 700 °C for 300 h in a gas mixture of H2S–H2–O2–Ar with a high partial pressure of S−2 and low partial pressure of O−2. Sulfidation resistance of FeAl coating was improved by the addition of 2–5 wt.% CeO2, which inhibits the outward diffusion of Fe, acts as traps for sulphur in splat boundaries, and slows down the depletion of Al in the coating. The corrosion products were found to consist of FeS and Fe1−XS on the pure FeAl coatings, but primarily Fe1−XS on FeAl coatings with 2–8% CeO2. The addition of 8 wt.% CeO2 induced thermal cracks and hence decreased sulfidation resistance. The optimum amount of CeO2 addition in FeAl in terms of sulfidation resistance is suggested to be 2–5 wt.%.

High Temperature Sulfidation Resistance of DO3 - Ordered FeAl Tested in H2S-rich Gases

AbstractThe sulfidation behaviour at 973 K in a 30 vol.% H2S-H2-H2O-N2 gas mixture of Fe-25 % at. Al, DO3-ordered alloys, binary or alloyed with niobium, was investigated. Binary alloys presented a quite good sulfidation resistance in comparison with 321 stainless steel, even if a large amount of iron sulfides FeS grew over the alumina layer on corroded samples. The sulfidation resistance of DO3 alloys could be significantly improved by an oxidation treatment prior to corrosion test. The Nb in iron aluminides was supposed to preferably react with S and therefore, to enhance sulfidation resistance through preventing the nucleation and growth of harmful FeS. Unfortunately, the scales of Nb-allloyed FeAl contained only a small amount of Nb3S4 which did not prevent efficiently the formation of iron aluminides FeS. Adding Nb to Fe-25Al even resulted in a severe deterioration of the microstructure during sulfidation due to intense diffusion of S inward the sample.

Al enrichment of carbon steels through weld overlay process for improved oxidation resistance

A simple method is described for enriching the surface aluminum concentration of carbon steel. The process of weld overlaying steel substrate with pure aluminum wire results in an aluminum concentration of ∼15–17 at.% (8–9 wt.%) for depths of ∼2 mm. The aluminum-enriched surface shows an improved oxidation and sulfidation resistance. The paper gives details of the process along with microstructural analysis and oxidation resistance improvement results.

ナトリウム-硫黄電池の概要と高クロム-鉄合金プラズマ溶射皮膜の耐硫化腐食性

ナトリウム-硫黄電池の概要と高クロム-鉄合金プラズマ溶射皮膜の耐硫化腐食性

Sulfidation behavior of Fe–40Al sheet in H 2–H 2S mixtures at high temperatures

The sulfidation behavior of a 200 μm thick Fe–40at.%Al sheet has been investigated at temperatures between 973 K and 1273 K in H 2–H 2S mixtures with H 2S contents of 0.052–9.7vol%. The Fe–40Al sheet exhibited excellent sulfidation resistance at temperatures below 1073 K in all the H 2S–H 2 mixtures. This may be attributed to the formation of a thin alumina film on the surface of the Fe–40Al sheet during sulfidation, identified by AES analysis. At temperatures higher than 1173 K, the Fe–40Al sheet also exhibited good sulfidation resistance in the 0.052%H 2S–H 2 mixture, and there was only a slight increase in mass gain with temperature. This compares favorably with Fe–20Cr–11Al (in at.%) foil which was severely sulfidized even at 973 K in the 0.052%H 2S–H 2 mixture, and showed markedly increased mass gain with increased H 2S content and temperature.

Effect of pre-oxidation on high temperature sulfidation behavior of FeCr and FeCrAl alloys

High temperature corrosion of structural alloys in sulfur bearing environments is many orders of magnitude higher than in oxidizing environments. Efforts to increase sulfidation resistance of these alloys include addition of alloying elements. Aluminum additions to iron-chromium alloys bring about increase in sulfidation resistance. This paper reports the effect of pre-oxidation on the sulfidation behavior of Fe-20Cr and Fe-20Cr-5Al alloys in H2-2% H2S environment at 800 °C. The surfaces of sulfidized specimens were also examined. Pre-oxidation of the two alloys results in an incubation period during subsequent sulfidation. After this incubation period, the Fe-20Cr alloy showed sulfidation behavior similar to that when the alloy was not pre-oxidized. The incubation period during sulfidation of the Fe-20Cr-5Al alloy was significantly longer, over 45 h, compared to 2 h for the Al free alloy. Based on the microscopic and gravimetric data a mechanism for sulfidation of these alloys with pre-oxidation has been proposed.

INCONEL ALLOY 693

Abstract This alloy improves upon the excellent high-temperature corrosion resistance of INCONEL alloy 690 (see Alloy Digest Ni-266, March 1981) through an addition of aluminum. Inconel Alloy 693 is typically 61% Ni, 29% Cr, 3.3% Al, and 0.7% Nb, with the balance being principally iron. By virtue of its contents of chromium and aluminum, alloy 693 offers particularly good resistance to oxidation, carburization, sulfidation, and special resistance to metal dusting. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming and heat treating. Filing Code: Ni-617. Producer or source: Special Metals Corporation.

Sulfidation Kinetics of FeCr and FeCrY Alloys

The sulfidation behavior of Fe20Cr and Fe20Cr0.7Y alloys in H2–H2S atmospheres at 700 and 800°C was determined by thermogravimetry. Isothermal measurements were carried out and the sulfidation kinetics were evaluated from the mass gain vs. time curves. The reaction products were examined in a scanning electron microscope and the compositions of micro-regions were determined using energy dispersive spectroscopy and X-ray diffraction. Yttrium addition increased the sulfidation resistance of the FeCr alloy.

873KにおけるNi基超合金の耐硫化性に及ぼすTiおよびAl添加量の影響

873KにおけるNi基超合金の耐硫化性に及ぼすTiおよびAl添加量の影響