The intercrystalline corrosion had appeared on the superheater and reheater with Super304H steel tubes

leading to leakage at many locations.The cracked Super304H steel tubes have been sampled

through chemical components analysis

energy spectrum analysis

as well as observation of metallographic structure and using scanning eletron microscope etc.

the causes leading to intercrystalline corrosion of said steel tubes have been obtained.Results show that the basic body of Super304H steel is isoaxial austenitic structure

regardless of sensibilization treanment or not

after test of crystalline corrosion and bending

cracks have appeared.The ratio between niobium content and carbon content is only 5.4

the higher corbon content and lower niobium content are easy to result in intercrystalline corrosion.