Abstract
Fireside corrosion behavior of austenitic heat-resistant steel 10Cr18Ni9Cu3NbN was investigated which was firstly applied in a 660 MW power plant. XRD, SEM and EDS were utilized to characterize the corrosion products and to reveal the corrosion mechanism. Results show that corrosion products formed on experimental tubes were composed of a molten salt layer (MSL), a metallic oxidation layer (MOL) and an internal sulfuration zone (ISZ). A thick MSL containing a mixture of spherical AlSi oxides/ CaSO4 and Fe2O3 is formed above Fe- and Cr-rich oxide scales. Fe and Cr sulfides are found underneath the MOL, which are developed at high pressure of sulfur. The corrosion rate at fireside facing the flue gas is much greater than that on the reverse side. Strict control of sulfur content in coal was therefore proposed relieving fireside corrosion of heat-resistant steels. The corrosion mechanism is put forward. Lastly, the exfoliation of MSL is caused by aggregate CaSO4 particles.
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