The current service situation of such materials as T23

T91 and TP347H steel used for pipes on final superheater of the first generation domestic 600 MW supercritical boiler was analyzed.Steam oxidation was considered as the major factor that affect the safe and stable operation of the final superheater pipes.The principles for pipe upgrading was proposed:the highest wall temperature of T23 steel pipes should be lower than 570 ℃;that of the T91 steel pipes should be lower than 600 ℃;while for pipe segment where the wall temperature is between 600 ℃ to 640 ℃

the TP347H steel after inner shot peening or fine-crystalline TP347HFG steel should be used.Several advices on material selection for steam oxidation resistance temperature based pipe retrofitting were proposed.