High temperature corrosion mechanisms of certain new TiAl-based intermetallic alloys in an aggressive H2/H2O/H2S environment at 850°C

This paper discusses the sulphidation/oxidation protection offered by multilayer CrAlYN/CrN coatings etched by Cr, CrAl and Y ions, deposited by a combined high power impulse magnetron sputtering (HIPIMS)/unbalanced magnetron sputtering (UBM) technique on a Ti–45Al–8Nb alloy (at%). The test was performed at 750 °C in an environment of H2/H2S/H2O yielding low oxygen (10−18 Pa) and high sulphur (10−1 Pa) partial pressures for up to 1000 h. The results show that all the exposed materials underwent uneven degradation; some places developed a thin protective oxide scale (Al,Cr)2O3 with a tiny sulphur content, whilst others developed a porous non‐protective TiO2 + Al2O3 scale as well with a tiny sulphur content.

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“…The morphology and the scale structure formed on the exposed alloy is in good correlation with the results presented by other researches .…”

Section: Resultssupporting

confidence: 88%

“…In contrast, darker area suggests a low concentration of the element. Similar to this work, other studies also reported the formation of TiO 2 , NbS 2 and NbAl 3 phases at the coating–alloy interface, or under the oxide scale of the uncoated alloy .…”

Section: Resultssupporting

confidence: 88%

Enhanced sulphidation/oxidation resistance of Ti–45Al–8Nb alloy by nanostructured CrAlYN/CrN coatings at 750 °C

Dudziak

Datta

et al. 2012

Materials & Corrosion

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“…This supposition is consistent with the Al 2 O 3 -rich mixed scales typically reported for TiAl-base alloys under sulfidation-oxidation conditions (minor amounts of Al, Ti sulfides were also reported)[27][28][29].…”

supporting

confidence: 79%

“…A key question is therefore why TiCrAl was so much more resistant than FeCrAl, i.e., why does the third-element effect, as defined above, apparently still operate for TiCrAl but not for FeCrAl in the presence of H 2 S? TiAl alloys are generally reported to exhibit good sulfidation-oxidation resistance [27][28][29]. This does not appear to directly result from an inherently superior resistance of Ti as an alloy base as compared with Fe under these conditions.…”

mentioning

confidence: 99%

Sulfidation–Oxidation Behavior of FeCrAl and TiCrAl and the Third-Element Effect

Brady

Tortorelli

et al. 2010

Oxid Met

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Short-term sulfidation-oxidation exposures were conducted under high pS 2 and low pO 2 conditions for TiCrAl and FeCrAl alloys at 600 and 800°C. Low mass gains and submicron Al-and Ti-rich oxide scales were formed on TiCrAl at 600°C, while high mass gains and FeS-based scale formation were observed for FeCrAl. Based on the good behavior of TiCrAl, third-element effect additions of Cr are not inherently detrimental under sulfidation-oxidation conditions. Rather, differences in the mechanistic action of the third-element addition of Cr between FeCrAl and TiCrAl alloys and its relevance to low oxygen potential sulfidationoxidation environments were the key factors in determining whether or not a protective alumina scale was established.

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“…Excellent mechanical properties are the crucial requirement for γTiAl alloys owing to their application in rotation parts in turbines. However, sufficient oxidation and corrosion resistance at high temperature might be concernful when service environment become severe 4 , especially as the targeting service temperature for γTiAl alloys become higher currently 5 . Therefore, extensive researches on the oxidation and corrosion behavior of γTiAl alloys under service environment have been undertaken [6][7][8][9][10][11][12][13][14][15][16][17] .…”

Section: Introductionmentioning

confidence: 99%

THE EFFECT OF HIGH TEMPERATURE CORROSION ON MECHANICAL BEHAVIOR OF A GAMMA-TiAl ALLOY

Zhao

Gong

2010

Int. J. Mod. Phys. B

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The mechanical properties of Ti-48Al-2Cr-2Nb alloy were discussed after the high temperature corrosion tests carried out with salt mixture of 75wt. % Na2SO4 and 25wt. % NaCl at 800℃. The microstructure of the alloy after corrosion was observed by SEM and the fracture behavior of the corroded and uncorroded alloys was investigated by means of the three-point bending tests. It has been shown that the corrosion path was mainly along the lamellar structure and rough surface with a large number of corrosion pits formed during the high temperature corrosion. The experimental results also indicated that the bearing capacity of bending fracture descended evidently due to the molten salt corrosion at high temperature, which only had remarkable effects on the surface state of the alloy. The microcracks inside the alloy always propagated along the phase interfaces and grain boundaries while the corrosion pits on salt-deposited surface became the main crack initiation location in corroded alloy. The stress concentration caused by corrosion was considered as the essential reason of the property reduction, which decreased the energy barrier of crack nucleation and shortened the incubation period.

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High temperature corrosion mechanisms of certain new TiAl-based intermetallic alloys in an aggressive H2/H2O/H2S environment at 850°C

Cited by 22 publications

References 27 publications

Enhanced sulphidation/oxidation resistance of Ti–45Al–8Nb alloy by nanostructured CrAlYN/CrN coatings at 750 °C

Enhanced sulphidation/oxidation resistance of Ti–45Al–8Nb alloy by nanostructured CrAlYN/CrN coatings at 750 °C

Sulfidation–Oxidation Behavior of FeCrAl and TiCrAl and the Third-Element Effect

THE EFFECT OF HIGH TEMPERATURE CORROSION ON MECHANICAL BEHAVIOR OF A GAMMA-TiAl ALLOY

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