Superheater tubes are subjected to the most severe combination of stress, temperature and corrosive environment. In addition to high-temperature strength, resistance to corrosion is also important. For example, low-alloy ferritic steel such as 2-1/2% Cr, 1% Mo would not be used at metal temperatures above 580°C because of inadequate resistance to corrosion and oxidation over a full service life of 100,000/150,000 hr.
Failures in superheater tubes may arise from :
(a) Prior fabrication history
(b) Faulty heat treatment
(c) Consequences of welding
(d) Overheating of the tube metal
(e) Gas-side corrosion
(f) Stress corrosion (austenitic steels).
Failures in superheater tubes may arise from :
(a) Prior fabrication history
(b) Faulty heat treatment
(c) Consequences of welding
(d) Overheating of the tube metal
(e) Gas-side corrosion
(f) Stress corrosion (austenitic steels).
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