Abstract
Ni–(35–45)Cr–4Nb alloys containing different fractions of α‐Cr were
exposed to potassium chloride (KCl)‐induced corrosion. The corrosion
exposures were carried out for 168 hr at 600°C in a 15% (vol/vol) H2O (g) + 5% (vol/vol) O2 (g) + N2
(g; balance) atmosphere using KCl‐free (reference) and predeposited KCl
samples. To mimic the KCl deposition in real boilers, 24 hr exposures
where KCl vapor condensed continuously onto samples were also performed.
The corrosion attack of the studied materials increased significantly
when KCl was present compared to the KCl‐free samples. For the KCl
exposures, the corrosion attack drastically increased when a significant
α‐Cr fraction was present. α‐Cr was either selectively attacked or
dissolved through solid‐state diffusion and a layered build‐up of the
outer external scale of K2CrO4 and chromia could
be observed. For the in situ condensed KCl exposure, severe corrosion
was observed already within the 24 hr exposure, indicating a higher
corrosion rate compared with when KCl was predeposited.
Original language | English |
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Journal | Materials and Corrosion |
Volume | 70 |
Issue number | 8 |
Pages (from-to) | 1486-1506 |
ISSN | 0947-5117 |
DOIs | |
Publication status | Published - 2019 |
Keywords
- KCl-induced high-temperature corrosion
- Ni–Cr–Nb alloys
- Phase dissolution
- Selective attack
- α-Cr