Study of the cyclic oxidation resistance of Al coated ferritic steels with 9 and 12%Cr (original) (raw)

Improvement of 9% Ferritic Steel Against Cyclic Oxidation by CVD-FBR Al–Mn Coating

Oxidation of Metals, 2008

Cyclic-oxidation tests were performed on uncoated and Al-Mn coated P92 stainless steels in air at 650°C. SEM and X-ray analyses revealed the formation of iron-chromium spinel, magnetite and hematite on uncoated steel, which spalled dramatically. The aluminized substrate promoted the formation of a continuous, adherent alpha-alumina scale. The formation of this protective alumina layer depended mainly on the characteristics of the initial aluminide coating. A coating with high aluminum content allowed the formation of an alumina oxide, which cracked easily during thermal cycling. The improvement of the cyclic-oxidation resistance was provided by the alumina scale obtained on the coating with lower Al content. COSP modeling showed good performance by surface coating. Aluminum coating is able to extend metal life by the delaying time to reach crossover.

Degradation of Aluminide Layers During Cyclic Oxidation of Ferritic 430 Stainless Steel

Jurnal Teknik Mesin, 2011

In order to increase the performance of the preferred Ferritic 430 SS for manufacturing automobile and motorcycle exhaust systems. The aluminizing coating on the surface of bare steel was applied by hot-dipping method in a molten pure aluminum. The high temperature oxidation of the aluminized steel was cyclically studied at 900 °C and 1000 °C in static air. The degradation of intermetallic layers during cyclic oxidation were analyzed by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The crack perpendicular to the specimen surface rapidly propagated through the FeAl and Fe3Al layers due to a thermal expansion mismatch upon cooling to room temperature. The accumulation of voids generated crack at the interface between the aluminide layer and the steel substrate. Oxygen is allowed to penetrate into the aluminide layer crack, rapidly forming alumina oxide and closing the crack. Some of the aluminide layers peeled off due to this rapid growth. Thus, the protective Al2O3 layer degraded and later, the substrate was oxidized subsequently to form iron-rich oxide (Fe2O3) at 1000 °C.

Cyclic oxidation of ASTM A53 grade B steel protected with a chromium alloy via thermal arc spraying

Contemporary Engineering Sciences

In this study, ASTM A53 grade B steel samples were coated with 13% chromium steels via electric arc thermal spraying (EATS); these samples underwent oxidation cycles at 500°C and 600°C. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XDR) were performed to study the composition, morphology, and structure of the chromium oxide (FeCr2O3) layer formed on the surface. Layers formed on the steel without coating were continuous, had low adherence, and mainly composed of Fe3O4 and γ-Fe2O3. Samples without coating exhibited high mass loss because protective oxides were not formed and oxide husk could be detached easily. Samples coated via EATS exhibited a good performance because of the presence of an anticorrosive FeCr2O3 layer, thereby presenting good adherence between the chromium layer and the substrate. This phenomenon prevented the oxide husk from detaching easily from the substrate.

High Temperature Oxidation of Fe-Cr-Al Coatings Prepared by Flame Spray Technique

Journal of Physics: Conference Series, 2019

In the present study, Fe-Cr and (Fe-Cr)-30at% Al coatings were prepared by a flame spray technique. The coated samples were then annealed in a vacuum furnace at 800 o C for 2h. The high temperature cyclic oxidation test was performed at 800 o C for up to 8 cycles to investigate its oxidation resistance. XRD and SEM-EDS were used to characterize the oxidized samples. The results showed that low carbon steel was susceptible to oxidation at this temperature. Thick Fe oxides layer was formed on the steel surface. On the contrary, Fe-Cr-Al coating showed an increase in oxidation resistance of low carbon steel. The FeCr coating with 30 at % Al content exhibited the lowest mass gain after exposure for 8 cycles at 800 o C.

High Temperature Cyclic Oxidation Resistance of Iron Chromium Base Alloys

Chemical Engineering & Technology, 2010

The cyclic oxidation behavior of an experimental stainless ferritic steel, without molybdenum and with copper-aluminum-titanium-lanthanum additions, developed for solid oxide fuel cell applications, was evaluated and compared with the oxidation behavior of commercial austenitic and ferritic stainless steels. For the cyclic oxidation tests, the steel samples were tested at temperatures ranging from 600 to 800°C. The experimental ferritic stainless steel showed the highest cyclic oxidation behavior among the studied steels at 700°C and 800°C, presenting a parabolic and logarithmic kinetics, respectively.

Cyclic Oxidation of Heat Resisting Steels

Oxidation of Metals, 2005

Standard cast, heat resisting steels containing 25-29 w/o (weight percent) chromium and 30-36 w/o nickel together with cast alloys containing 45 or 60 w/o nickel plus low levels of aluminium were subjected to cyclic oxidation in air at 1000 and 1150 • C. The standard materials suffered rapid weight loss which was somewhat mitigated by the presence of cerium. The 45 w/o nickel alloys were much more resistant and the 60 w/o nickel alloys showed superior resistance to cyclic oxidation. This improvement was due to alumina formation at or near the alloy surface. In the absence of aluminium, alloys underwent subsurface chromium carbide oxidation at a rate independent of alloy chromium content. This effect is shown to be a consequence of rapid oxygen diffusion along internal phase boundaries.

Microstructure studies of an aluminide coating on 9Cr-1Mo steel during high temperature oxidation

Surface and Coatings Technology, 2006

9Cr-1Mo steel coated by hot-dipping into a molten mixture with 7wt.%Si/93wt.%Al was oxidized at 750, 850, and 950°C in static air. The oxidation kinetics followed a parabolic rate law at all temperatures. Intermetallic iron-aluminum compounds FeAl 3 , Fe 2 Al 5 , and FeAl 2 initially formed on the steel substrate at elevated temperature. At 850°C the Fe x Al y layer thickness increased rapidly during the first 20 min and Fe 2 Al 5 mixed with FeAl 2 became the main phases in the aluminide layer. Some cracks propagated through the Fe x Al y brittle FeAl 2 and Fe 2 Al 5 layers. After 24 h oxidation at 850°C, all FeAl 2 +Fe 2 Al 5 transformed to FeAl, while FeAl 2 +Fe 2 Al 5 still existed at 750°C after 56 h exposure. The Kirkendall effect is a plausible mechanism for the voids observed at the interface between the aluminide layer and the steel substrate.

Cyclic high temperature oxidation behaviour of bare and NiCr coated mild steel and low alloyed steel

Elsevier : Materials Today Proceeding, 2018

Oxidation behaviour of low carbon and low alloyed steels at different Ni-Cr coatings thickness are studied, and also investigated the resistance offered by different coating thickness. Hardness of low alloy steel was increased from 202 to 342 VHN whereas that of mild steel was increased from 148 to 309 VHN after the application of coatings. Parabolic rate constant (Kp) for high temperature oxidation of bare, 200-250µm, and 250-300µm thick Ni-Cr coated low alloy steel were calculated to be 787.192, 0.235608, and 0.501787 (×10-10g2cm-4s-1) respectively, whereas that of mild steel were calculated to be 1104.49, 0.0309172, and 0.0978113 (×10-10 g2cm-4s-1) respectively.

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.

Effect of surface finishing on the oxidation behaviour of a ferritic stainless steel

Applied Surface Science, 2017

The corrosion behaviour and the oxidation mechanism of a ferritic stainless steel, K41X (AISI 441), were evaluated at 800 • C in water vapour hydrogen enriched atmosphere. Mirror polished samples were compared to as-rolled K41X material. Two different oxidation behaviours were observed depending on the surface finishing: a protective double (Cr,Mn) 3 O 4 /Cr 2 O 3 scale formed on the polished samples whereas external Fe 3 O 4 and (Cr,Fe) 2 O 3 oxides grew on the raw steel. Moreover, isotopic marker experiments combined with SIMS analyses revealed different growth mechanisms. The influence of surface finishing on the corrosion products and growth mechanisms was apprehended by means of X-ray photoelectron spectroscopy (XPS) and residual stress analyses using XRD at the sample surfaces before ageing.