在役12Cr1 MoV钢管材的性能劣化及其损伤机制

Performance Degradation and Damage Mechanisms of in Service 12Cr1MoV Steel Pipe

对某热电厂在役主蒸汽管母材12Cr1MoV试样进行了短时力学性能测试,对试样的金相和断口进行了电子显微图谱分析,评价并研究了管材在高温下的蠕变损伤及断裂失效机制.分析结果表明:使用管常温冲击韧性的剧减可归因于微裂纹的迅速扩展;应变率较小的失效过程则由孔洞的聚集生长和管材有效截面的减缩机制控制;Cr,Mn等合金元素在晶界碳化物中的富集度可作为表征材料损伤形核程度的参数,并用以估算损伤孕育时间.

Shortterm mechanical tests were conducted for 12Cr1MoV steel specimens(parent material) taken from an inservice main steam pipe of a power plant. Metallographic examinations and fractographic analyses were carried out for the cut specimens. Creep damage and failure mechanisms of the pipe material at elevated temperature were evaluated and studied. The results show that (1) the sharp reduction of impact toughness of the inservice material at normal temperature can be attributed to the fast growth of inner microcracks under impact; (2) the mechanisms such as creep cavity accumulating and effective crosssection shrinking of the pipe dominate the process of low strain rate failure; and (3) the degree of enrichment of constituent elements such as Cr and Mn in the grain boundary carbides can be used as a parameter to characterize the damage nucleation, then, to estimate the damage incubation time.