Influence of Water Vapour on Isothermal and Thermal Cyclic Oxidation Conditions of a Nickel-Based SY625 Steel at 1100°C

2012 ◽  
Vol 323-325 ◽  
pp. 333-338
Author(s):  
Raphaël Rolland ◽  
Henri Buscail ◽  
Christophe Issartel ◽  
Frédéric Riffard ◽  
Françoise Rabaste ◽  
...  
Keyword(s):  
Grain Size ◽  
Oxide Scale ◽  
Water Vapour ◽  
Cyclic Oxidation ◽  
Isothermal Oxidation ◽  
Chromia Scale ◽  
Scale Spallation ◽  
Oxidation Condition ◽  
Dry Conditions ◽  
Dry And Wet Conditions

In isothermal oxidation condition, water vapour has little effect on the oxidation rate and scale composition of a nickel-based SY 625 alloy oxidized at 1100°C. The scale is composed of an outer Cr2O3and an internal CrNbO4scale. The oxide scale morphology differs between dry and wet conditions. Under dry conditions the oxide scale appears to be compact and chromia pegs are observed at the internal interface. Under wet conditions, porosities are observed spread inside the scale and the chromia grain size is smaller. At this temperature some scale spallation is observed under dry and wet conditions. Under cyclic oxidation conditions the oxide scale adherence is slightly improved in wet environment. The chromia scale is adherent during the 4 first oxidation cycles. In dry air, spallation occured after the first cycle. In dry and wet conditions, after the chromia scale spallation has started, NiO and NiCr2O4form first. NiMoO4forms later on the alloy surface during the cycling test. The best resistance of the alloy under thermal cycling conditions under wet conditions is related to the presence of a more plastic and adherent scale owing to a higher scale porosity and smaller chromia grain size compared to dry conditions.

Influence of Water Vapour on a Nickel-Based Alloy Oxidation

2012 ◽  
Vol 323-325 ◽  
pp. 309-314
Author(s):  
Henri Buscail ◽  
Raphaël Rolland ◽  
Christophe Issartel ◽  
Frédéric Riffard ◽  
Françoise Rabaste ◽  
...  
Keyword(s):  
Oxide Scale ◽  
Water Vapour ◽  
Scale Spallation ◽  
Internal Interface ◽  
Alloy Oxidation ◽  
Influence Of Water ◽  
Dry Conditions ◽  
Nickel Based Alloy ◽  
Dry And Wet Conditions ◽  
Scale Composition

Water vapour has little effect on the oxidation rate and scale composition of a nickel-based SY 625 alloy oxidized between 900 and 1100°C. At 900 and 1000°C, the outer scale is composed of Cr2O3 and a continuous NbNi4 - Ni3Mo subscale is found at the oxide/alloy interface. At 1100°C the scale is composed of an outer chromia scale and an internal CrNbO4 subscale. The oxide scale morphology differs between dry and wet conditions. Under dry conditions the oxide scale appears to be compact and chromia pegs are observed at the internal interface. Under wet conditions, porosities are observed inside the scale. At 1100°C some scale spallation is observed under dry and wet conditions.

Effect of Hf Content on Oxidation Resistance of Single Crystal Superalloy at 1000°C

2014 ◽  
Vol 915-916 ◽  
pp. 562-566 ◽  
Author(s):  
Z.X. Shi ◽  
Shi Zhong Liu ◽  
M. Han ◽  
J.R. Li
Keyword(s):  
Grain Size ◽  
Single Crystal ◽  
Oxide Scale ◽  
Oxide Layer ◽  
Oxidation Resistance ◽  
Isothermal Oxidation ◽  
Single Crystal Superalloy ◽  
Ambient Atmosphere ◽  
Directionally Solidified ◽  
Better Than

The specimens of single crystal superalloy DD6 with 0.10% Hf and 0.47% Hf were prepared in the directionally solidified furnace. The effect of Hf content on the isothermal oxidation resistance of the second generation single crystal superalloy DD6 was studied at 1000°Cin ambient atmosphere. Morphology of oxides was examined by SEM, and their composition was analyzed by XRD and EDS. The experimental results show that the oxidation resistance of DD6 alloy with 0.47% Hf is better than that of the alloy with 0.10% Hf. The alloy with different Hf content all obeys parabolic rate law during oxidation for 100h at 1000°C. The increase of Hf content can promote the Al2O3 formation and decreases the proportion of NiO. The oxide grain size and the thickness of the oxide layer all reduce with increasing of Hf content. The oxide scale of the alloy with different Hf content is made up of an outer NiO layer with a small amount of Co3O4, inner Al2O3 and Cr2O3 layer with a small amount of TaO2.

Corrosion Behavior of Fe-Cr Alloys in Ar-10%O2 Atmosphere

2011 ◽  
Vol 462-463 ◽  
pp. 1250-1254 ◽  
Author(s):  
Norinsan Kamil Othman ◽  
N. Othman ◽  
Azman Jalar
Keyword(s):  
Oxide Scale ◽  
Oxidation Rate ◽  
Cyclic Oxidation ◽  
Corrosion Behaviour ◽  
Optical Metallography ◽  
Chromia Scale ◽  
X Ray Diffraction ◽  
Breakaway Oxidation ◽  
X Ray ◽  
Cr Content

The corrosion of four Fe-Cr alloys (Cr: 9, 12, 20, and 25%) with different Cr contents were subjected to cyclic oxidation furnace in Ar-10%O2 atmosphere at 950oC for 120 h. The samples after oxidation were investigated by using X-ray diffraction (XRD), optical metallography and SEM/EDS. The results indicated that increasing Cr content reduced the oxidation rate and the scale cracking. Alloys with less Cr content occurred breakaway oxidation due to formation of Fe-rich oxide scale. However, a thin protective chromia scale was observed on alloys with Cr > 20%. The corrosion behaviour on Fe-Cr alloy was then discussed based on experimental observation.

Isothermal and Cyclic Oxidation of Ti-6Al-4V Alloy

2016 ◽  
Vol 369 ◽  
pp. 99-103 ◽  
Author(s):  
Min Jung Kim ◽  
Poonam Yadav ◽  
Dong Bok Lee
Keyword(s):  
Thermal Shock ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Oxide Scales ◽  
Scale Spallation ◽  
Excessive Stress

The Ti-6Al-4V alloy was oxidized isothermally and cyclically in air, and its oxidation behavior was compared with that of Ti metal. The isothermal oxidation at 800°C indicated that Ti-6Al-4V and Ti oxidized fast almost linearly, and the oxide scales that formed on Ti-6Al-4V and Ti were non-adherent. The cyclic oxidation indicated that Ti-6Al-4V oxidized faster than Ti at 600°C, and serious scale spallation occurred in Ti-6Al-4V compared to Ti at 800°C. The oxide scales that formed on Ti-6Al-4V and Ti after cyclic oxidation at 800°C delaminated into several pieces owing to excessive stress aroused by the repetitive thermal shock.

Long-Term, Cyclic Oxidation Behaviour of Alumina- and Chromia-Forming Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 1107-1114 ◽  
Author(s):  
Renata Bachorczyk Nagy ◽  
Richard J. Fordham
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Oxide Scale ◽  
Water Vapour ◽  
Oxidation Resistance ◽  
Cyclic Oxidation ◽  
Oxidation Behaviour ◽  
Reactive Elements ◽  
Funded Project

The oxidation resistance behaviour of a number of surface-treated FeCrAl commercial alloys and some model alloys of well-defined composition, incorporating a range of reactive elements in trace amounts, has been studied under thermal cyclic conditions in air with and without additions of water vapour. Additions of reactive elements such as Zr, La, Y, Hf modify the oxidation resistance behaviour of FeCrAl-alloys by improving the scale adherence and consequently may extend the lifetime of FeCrAl steels. The presence of the water vapour can affect oxidation in a number of different ways. Our results may indicate that high content of water vapour can cause the lives of such alloys to be decreased. This work forms part of a larger European-funded project to evaluate physical properties, microstructural features, oxidation/corrosion resistance and lifetime improvement. The correlation between alloy parameters and lifetime; as well as the modeling of oxide scale behaviour as function of cycling conditions is also studied.

The Cyclic Oxidation behavior of Oxide-Dispersed β-NiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
B. A. Pint ◽  
L. W. Hobbs
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Cyclic Oxidation ◽  
Isothermal Oxidation ◽  
Short Term ◽  
Scale Spallation ◽  
X Ray ◽  
Transmission Electron ◽  
Nial Alloy ◽  
Scanning Transmission ◽  
La Addition

AbstractShort-term cyclic oxidation tests were performed at 1200°C and 1500°C on ²-NiAl with 1 vol% oxide dispersions of Y2O3, La2O3 and Al2O3. The Y2O3 addition resulted in a very adherent ±-Al2O3 scale at 1200°C, with some improvement in the scale adhesion at 1500°C, compared to an undoped ²-NiAl alloy. The La2O3 and Al2O3 additions resulted in more severe oxidation than the undoped ²-NiAl at 1200°C. Both Y and La ions are found to segregate to ±-Al2O3 scale grain boundaries using scanning transmission electron microscopy/energy dispersive x-ray analysis. However, at both 1200°C and 1500°C, the La addition appears to cause a rapid increase in the isothermal oxidation rate, leading to excessive scale spallation.

Evaluation of Nanocrystalline Coatings for Coal-Fired Ultrasupercritical Boiler Tubes

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
N. S. Cheruvu ◽  
R. Wei ◽  
M. R. Govindaraju ◽  
D. W. Gandy
Keyword(s):  
Oxide Scale ◽  
Internal Oxidation ◽  
Cyclic Oxidation ◽  
Thermal Exposure ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Al2o3 Scale ◽  
Scale Spallation ◽  
Al Content ◽  
Ultrafine Grain Structure

Cyclic oxidation behavior and microstructural degradation of nanocrystalline Ni–20Cr–xAl (where x=4 wt %, 7 wt %, and 10 wt %) coatings have been investigated. The coatings were deposited on Haynes 230 samples using a magnetron sputtering technique. Cyclic oxidation tests were conducted on the uncoated and coated samples at peak temperatures of 750°C and 1010°C for up to 2070 thermal cycles between the peak and room temperatures. The results showed that a dense Al2O3 scale was formed on the external surface of all coatings after exposure at both temperatures. All three coatings showed no evidence of internal oxidation after exposure at 750°C. Among the three coatings, only the coating containing 4 wt % Al showed evidence of internal oxidation along the columnar grain boundaries after exposure at 1010°C. The Al2O3 scale exhibited good spallation resistance during cyclic oxidation tests at both temperatures. As the Al content in the coating increased from 4 wt % to 7 wt % or 10 wt %, thermal exposure led to precipitation of coarse Al-rich particles at the coating/substrate interface. In addition, thermal exposure at both temperatures led to rapid depletion of Al in the coating and grain coarsening of the coatings. The improvement in oxide scale spallation resistance and accelerated depletion of aluminum are attributed to the ultrafine grain structure of the coating and oxide scale.

Evaluation of Nanocrystalline Coatings for Coal-Fired Ultra-Supercritical Boiler Tubes

2009 ◽  
Author(s):  
N. Sastry Cheruvu ◽  
Ronghua Wei ◽  
Madhavrao Govindaraju ◽  
David W. Gandy
Keyword(s):  
Oxide Scale ◽  
Internal Oxidation ◽  
Cyclic Oxidation ◽  
Thermal Exposure ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Al2o3 Scale ◽  
Scale Spallation ◽  
Al Content ◽  
Ultrafine Grain Structure

Cyclic oxidation behavior and microstructural degradation of nanocrystalline Ni-20Cr-xAl (where x = 4, 7, and 10 wt.%) coatings have been investigated. The coatings were deposited on Haynes 230 samples using a magnetron sputtering technique. Cyclic oxidation tests were conducted on the coated and uncoated samples at peak temperatures of 750°C and 1010°C for up to 2070 thermal cycles between the peak and room temperatures. The results showed that a dense Al2O3 scale was formed on the external surface of all coatings after exposure at both temperatures. All three coatings showed no evidence of internal oxidation after exposure at 750°C. Among the three coatings, the coating containing 4 wt.% Al only showed evidence of internal oxidation along the columnar grain boundaries after exposure at 1010°C. The Al2O3 scale exhibited good spallation resistance during cyclic oxidation tests at both temperatures. As the Al content in the coating increased from 4 to 7 or 10 wt.%, thermal exposure led to precipitation of coarse Al-rich particles at the coating/substrate interface. In addition, thermal exposure at both temperatures led to rapid depletion of Al in the coating and grain coarsening of the coatings. The improvement in oxide scale spallation resistance and accelerated depletion of aluminum are attributed to the ultrafine grain structure of the coating and oxide scale.

Effect of substrate thickness on oxide scale spallation for solid oxide fuel cells

2011 ◽  
Vol 53 (7) ◽  
pp. 2406-2412 ◽  
Author(s):  
W.N. Liu ◽  
X. Sun ◽  
E. Stephens ◽  
M. Khaleel
Keyword(s):  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Oxide Scale ◽  
Solid Oxide ◽  
Substrate Thickness ◽  
Oxide Fuel ◽  
Scale Spallation

Effects of Yttrium on Cyclic Oxidation Resistance of Co-10Cr-5Al Alloy at 700 °C

2014 ◽  
Vol 528 ◽  
pp. 25-29
Author(s):  
Ling Yun Bai ◽  
Xian Chao Xu ◽  
Jun Huai Xiang ◽  
Yun Xiang Zheng ◽  
Jun Wang
Keyword(s):  
Oxide Scale ◽  
Oxidation Resistance ◽  
Oxidation Rate ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Adhesive Property ◽  
Complex Mode ◽  
Rate Law ◽  
Parabolic Rate

The cyclic oxidation behavior of Co-10Cr-5Al alloys in atmosphere at 700 °C was investigated. The addition of 0.3 at.% Y changed the oxidation behavior from the approximate parabolic rate law to complex mode. The scale grown on the surface of Co-10Cr-5Al cracked seriously, while the oxide scale the Y doped alloy had better adhesive property. Yttrium doped in the sample promoted the forming of continuous Al2O3layer and decreased the oxidation rate of Co-10Cr-5Al alloys.

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