热处理对T91耐热钢的组织结构及力学性能的影响

Influence of Heat Treatment on Microstructure and Mechanical Properties of T91 Heat Resistance Steel

研究了T91钢经700～800℃热处理后的组织结构及力学性能特点,特别是碳化物的长大对T91钢结构与性能的影响。结果表明:供货态T91钢是由板条状铁素体F及在其晶界、晶内弥散分布的M23C6型碳化物构成的回火索氏体组织;随热处理温度的升高和时间的延长,F发生回复、再结晶和晶粒长大;同时,碳化物逐渐在F晶界聚集;经800℃×58 h热处理,碳化物长大成1～3μm的大颗粒,弥散度降低,从而导致T91钢的强度、硬度降低,而塑性、韧性提高。热处理态T91钢具韧窝聚集型断裂机制,塑性断裂特征较供货态明显。

Microstructure and mechanical properties of T91 steel heat-treated at 700 ～800 ℃ for various times were studied.The effects of carbide growth on microstructure and mechanical properties of T91 steel were also studied.The results show that the supplied T91 steel consists of lath ferrites（F） and M23C6 type carbides.As increasing the annealing temperature and time,the recovery,recrystallization and grain growth of the lath F takes place gradually;meanwhile,the M23C6 type carbides grow along the F grain boundaries.After annealed at 800 ℃ for 58 h,1～3 μm size carbide particles randomly distribute in the F matrix with a low dispersity.After annealing,the change of the microstructure of T91 steel increases the plasticity,toughness,but decreases the strength and hardness of the steel.The annealed T91 steel has a dimple-congregation type fracture mechanism with a higher plastic fracture characteristic than the supplied T91 steel.