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

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.