HR3C钢内压蠕变试验后显微组织与力学性能试验研究

Experimental Study on Microstructure and Mechanical Properties of HR3C Tubes After Internal Pressure Creep Test

研究了HR3C钢管试样在不同内压蠕变试验时间下显微组织和力学性能的变化,分析了HR3C钢析出相对力学性能的影响.结果表明:内压蠕变试验后,HR3C钢管试样晶内和晶界上均析出弥散分布的NbCrN相,此外M23C6碳化物在晶界形成连续链状分布,并随着试验时间的延长发生聚集和粗化,M23C6碳化物在晶内析出弥散分布的方形颗粒,在孪晶界以长板状析出;弥散分布的NbCrN相和M23C6碳化物以及晶界连续分布的M23C6碳化物产生弥散强化和晶界强化,导致内压蠕变试验后HR3C钢的强度和硬度均明显增大,随着试验时间的延长,不断聚集的M23C6碳化物弱化了晶界强化效果,使得HR3C钢抗拉强度略有下降;内压蠕变试验后,晶界连续分布的M23C6碳化物导致HR3C钢室温下冲击吸收功和断后伸长率明显减小.

Experimental studies were carried out on microstructure and mechanical properties of HR3C tubes after creep test at different internal pressures and time duration. Results show that dispersed NbCrN phases precipitate both within grains and on grain boundaries after internal pressure creep test; M23C6 carbides precipitate as a continuous chain on grain boundaries, which get coarsening with the increase of time duration; simultaneously, M23C6 carbides precipitate as square particles within grains and in the form of lath like phases on twin boundaries. The strength and hardness of HR3C tubes increase obviously after internal pressure creep test due to grain-boundary strengthening and dispersion strengthening from disperse phase precipitation of NbCrN and M23C6, and by continuously distributed M23C6 on grain boundaries, however, with the rise of time duration, M23C6 carbides on grain boundaries get coarsening, which result in a decrease of grain boundary strengthening, thus leading to a slight decrease of the tensile strength. Obvious decrease of both the room-temperature impact absorbing energy and the elongation of HR3C steel is resulted from the M23 C6 carbides continuously precipitated on grain boundaries after internal pressure creep test.