22Cr-25Ni奥氏体耐热钢高温时效的组织及性能

Mechanical and properties of austenitic heat resistant steel 22Cr-25Ni after high temperature aging

通过对新型22Cr-25Ni奥氏体耐热钢经650℃、700℃高温时效不同时间后进行硬度、室温拉伸、冲击试验,并利用光学显微镜、扫描电镜观察了其显微组织和室温冲击断口,研究了22Cr-25Ni钢时效后力学性能变化情况。结果表明,22Cr-25Ni钢经高温时效后,硬度、室温拉伸强度得到强化,在时效1000 h后达到最大值之后趋于稳定,22Cr-25Ni钢同时具有明显的时效脆性倾向,冲击吸收能量下降幅度较大,650℃时效100 h后冲击吸收能量由时效前的198 J下降到111 J,700℃时效100 h后冲击吸收能量仅为47 J,随着时效时间继续增加,当时效3000 h后冲击吸收能量减少到20 J,随后趋于稳定。22Cr-25Ni钢在高温时效后的力学性能变化主要是由CrNbN(Z相)、M23C6、MX这3种析出相的共同作用造成的。

Mechanical properties changes of a novel 22 Cr-25 Ni austenitic steel after aging at 650℃and 700℃were studied by means of hardness test,tensile test at room temperature,impact test,and the microstructure and impact fracture at room temperature were analyzed by means of optical microscope and scanning electron microscopy.The results show that the hardness and tensile strength are increased with aging time and reach maximum after aging for 1000 h,the aging embrittlement of 22 Cr-25 Ni steel is obvious,the impact absorbed energy is decreased to below 111 J after aging at 650℃for 100 h from 198 J before aging treatment,the impact absorbed energy is only 47 J after aging at 700℃for 100 h,and with the continuation of aging time,the impact toughness decreases to about 20 J after 3000 h aging and then tends to be steady.The change of mechanical properties is mainly caused by the precipitation phase of Cr Nb N,M23 C6 and MX after aging at high temperature.