Abstract:

Mechanical properties changes of a novel 22Cr-25Ni 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 22Cr-25Ni 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 CrNbN, M₂₃C₆ and MX after aging at high temperature.

Key words: 22Cr-25Ni steel, high temperature aging, precipitation phase, microstructure, properties