Predicting the depletion of chromium in two high temperature Ni alloys

Pillai, Rishi; Ackermann, H.; Lucka, K.

doi:10.1016/j.corsci.2012.11.040

Cited by 29 publications

(10 citation statements)

References 12 publications

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“…Holcomb studied the oxidation behaviour of alloys 625 and 230 in humid air at flow rates of 1.9 · 10 −3 and 7.6 · 10 −3 m/s at 760 °C and presented a methodology to calculate Cr‐evaporation rates from Cr 2 O 3 assuming a flat planar geometry. Pillai et al predicted the depletion of chromium in the NiCr‐based alloys 601 and 602 at 1000 °C exposed to a combustion atmosphere (2.55% O 2 , 11.7% H 2 O and 12% CO 2 in N 2 ) in a flame tube stabilised low‐NOx recirculation burner rig. Specimens were cut from the tube segments at the exhaust gas outlet where the temperature was 995 ± 15 °C and the average flow rate of the exhaust gases was calculated to be about 4.6 m/s.…”

Section: Discussionmentioning

confidence: 99%

Effect of gas flow rate on oxidation behaviour of alloy 625 in wet air in the temperature range 900–1000 °C

Huczkowski

Lehnert

Angermann

et al. 2016

Materials & Corrosion

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In many industrial processes, the flow rate of hot gaseous service environments may be in the range of several m/s. In the present paper, the effect of gas flow rate on the high temperature oxidation behaviour of alloy 625 in wet air is presented. The gas velocity was varied from near static conditions to linear gas flow rates up to 6 m/s. The oxidation kinetics were studied by gravimetry during cyclic/discontinuous testing at 900 and 1000 °C. The oxide scales and the subsurface depletion zones formed during exposure were studied by light optical microscopy, scanning electron microscopy with energy dispersive X‐ray analysis and, for selected specimens, by electron backscatter diffraction. It was found that Cr loss due to formation of volatile species is substantially enhanced by high gas flow rates thus significantly influencing the oxidation limited life time of the oxidising component. Within the studied range of flow rates no plateau value was reached, the Cr loss being substantially larger at a flow of 6 m/s than at 0.7 m/s. Additionally, it was found that geometrical factors of the test specimen substantially affected the extent of volatile species formation. Especially the leading edge of the specimen exhibited more extensive Cr loss than the other specimen areas.

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Section: Discussionmentioning

confidence: 99%

Effect of gas flow rate on oxidation behaviour of alloy 625 in wet air in the temperature range 900–1000 °C

Huczkowski

Lehnert

Angermann

et al. 2016

Materials & Corrosion

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“…After short‐time oxidation (ignoring the depletion of protective element such as Cr ), the increase in total impedance values of the oxidized compared to the unoxidized alloys demonstrates that thick high‐temperature oxide layers are protective barriers against electrochemical dissolution. Differences in EIS between intersecting and longitudinal surfaces are not significant, while differences in E corr and i corr are.…”

Section: Resultsmentioning

confidence: 99%

Influence of orientation on corrosion behavior of directionally solidified cobalt‐base superalloy

Zhang

2015

Materials & Corrosion

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Oxidation behavior on intersecting and longitudinal surfaces of directionally solidified cobalt‐base superalloy DZ40M was studied respectively at 1050 °C for 0.1 h, 1 h and 10 h and electrochemical property before and after oxidation on two orientations in 3.5% sodium chloride solution at room temperature was investigated. Grain boundaries of DZ40M are conducive to ion diffusion at elevated temperature and the higher area fraction of grain boundaries on intersecting surface results in higher oxidation rate and more CoO in the oxide layers. Carbides with Cr depletion zone around vulnerable to corrosion are located in grain boundaries, and unoxidized intersecting surface with higher area fraction of grain boundaries is prone to more serious uneven general corrosion. After oxidation, the corrosion resistance of the alloy is enhanced because oxide layer preferentially covers the grain boundaries and relieves the unevenness of corrosion. The protective effect of oxide layer is mainly provided by the innermost compact and continuous chromium oxide (Cr2O3). The intersecting surface has lower Ecorr and higher icorr, for the protective Cr2O3 layer on this orientation is largely consumed by excessive cobalt oxide to form CoCr2O4.

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“…The critical depletion of Cr in the alloys 740H, 282 and 625 during exposure in high pressure sCO 2 (300 bar sCO 2 ) between 700-800 °C was employed as corrosion-induced lifetime criteria. Beyond the accepted critical Cr depletion of 10 wt.% [13,14] at the interface between the external Cr 2 O 3 scale and the Ni-based alloy, formation of other faster-growing and non-protective oxides such as Ni-, Fe-and Ti-rich oxides is expected. Additionally, the loss of sound metal due to corrosion will be critical for thin components since the metal loss can be comparable to the initial component thickness.…”

Section: Subtask 11: Identifying Materials Based On Chosen Applicationmentioning

confidence: 99%

“…However, it has been shown previously that a protective external chromia formation can most likely not be sustained below a critical value of Cr concentration at the scale\alloy (O\M) interface. The critical value was given to be 10 wt.% [13,45] for chromia-forming Ni-based alloys. The concentration of Cr at the scale\alloy interface is governed by its consumption due to oxidation (oxidation kinetics) and its rate of transport from the alloy to the O\M interface (diffusion coefficient).…”

Section: Subtask 21: Integrate Models To Describe Physics For Degrada...mentioning

confidence: 99%

Development of an Open-source Alloy Selection and Lifetime Assessment Tool for Structural Components in CSP

Pillai¹,

Romedenne²,

Lee³

2022

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Predicting the depletion of chromium in two high temperature Ni alloys

Cited by 29 publications

References 12 publications

Effect of gas flow rate on oxidation behaviour of alloy 625 in wet air in the temperature range 900–1000 °C

Effect of gas flow rate on oxidation behaviour of alloy 625 in wet air in the temperature range 900–1000 °C

Influence of orientation on corrosion behavior of directionally solidified cobalt‐base superalloy

Development of an Open-source Alloy Selection and Lifetime Assessment Tool for Structural Components in CSP

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