High‐temperature corrosion behavior of S30432 and TP310HCbN coatings in simulated 620°C ultra‐supercritical boiler coal ash/gas environment

Abstract

The high‐temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620°C ultra‐supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650°C and 700°C, respectively, for 2000 h. The samples are then analyzed through X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. S30432 is mainly oxidized under 650°C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm−2. However, under 700°C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high‐temperature corrosion. As a result, weight reduction up to 41.8 mg cm−2 occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm−2 is observed. After 11 520 h of the actual operation of the 1000 MW 620°C boiler, there is no obvious high‐temperature corrosion in the high‐temperature areas without coke‐block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620°C ultra‐supercritical boilers burning high‐sulfur coal.