Research Progress on High Temperature Materials for 700 ℃ Ultra-Supercritical Coal-Fired Unit

Nowadays, the materials research for 700 ℃ ultra-supercritical coal-fired unit is focused on the component materials with high-temperature strength all over the world. The microstructures, mechanical properties and research progress of the materials used for water wall tube, superheater/reheater tube, main steam pipe and high-temperature steam header in the unit are introduced. HCM12 steel and Inconel alloy 617 can be used for high temperature section of water wall tube. Inconel alloy 740H is produced by modification of Inconel alloy 740 and can be used to fabricate superheater/reheater tube, main steam pipe and high-temperature steam header due to its high creep rupture strength and excellent welding performance. In the future research, it is important to verify the high temperature creep rupture strength and creep strength of as-mentioned alloys in practice; meanwhile the optimum heat working process should be studied to improve the heat working property and welding performance and reduce the cost of material.