电站用9Cr钢长时时效组织演变及冲击性能

摘要：以9Cr钢为研究对象，系统研究620℃长时时效过程中的组织演变及冲击功变化规律。结果显示，未经时效处理（原始态）的9Cr钢室温冲击功测试值为140J左右。经过长时时效处理（时效态）的9Cr钢室温冲击功降低至30J左右。原始态9Cr钢中的析出相以M23C6型碳化物为主，尺寸在100～200nm之间。时效态9Cr钢中部分M23C6相长大至500nm，且存在脆性Laves相。M23C6相的长大和Laves相的出现，在削弱合金元素的固溶强化作用的同时也造成沉淀强化作用的降低，导致高温长时时效处理后的9Cr钢的冲击性能降低。高温长时时效后的析出相整体尺寸细小且无明显聚集，表现出良好的组织稳定性。室温冲击功与时效时间的关系式（W=129.7exp(-t/1193.4)+25.

Microstructure evolution and corresponding impact property during long term aging of 9Cr martensitic heat resistant steel used in power plant

Abstract： The microstructure evolution and corresponding impact energy of the 9Cr steel aged at 620℃ were systematically investigated. The results show that the impact energy of the 9Cr steel without aging (original state) is around 140J, and it gradually decreases to about 30J with the increased aging time. The microstructures observed by scanning electron microscopy (SEM) illustrate that the main precipitates for 9Cr steel in the original and long term aged states are both M23C6 type carbides. Some M23C6 type carbides increase from 100-200nm to 500nm after the 9Cr steel being aged. The Laves phase could also be detected in the aged 9Cr steel. The growth of partial M23C6 type carbides and the formation of Laves phase during the long term aging process could simultaneously weaken both the precipitation and solution strengthen effects rooted at the alloy elements, causing the decrease of the impact energy eventually. Though the partial carbides in 9Cr steel are coarsened during the long term aging treatment at elevated temperature, most of the precipitates are kept nearly unchanged without forming chain structure, exhibiting excellent high temperature stability. Based on the equation of W=129.7exp(-t/11934)+25.6 between the impact energy and aging time, the satisfied impact energy can still be anticipated for 9Cr steel even with longer aging time.