Abstract��The P91 heat resistant steel (10Cr9MoVNb) was the required steel in supercritical (ultra-supercritical) generator set. Since the working temperature of main-steam pipeline was 600 ��, the creep behavior of P91 heat resistant steel at this temperature was investigated. The test was conducted at stress of 140 MPa. The creep fracture time was 5 534 h and the creep rate was 0.2 ��m/h. Then, the creep test was conducted under same conditions for 100 h and 1 800 h, which was corresponding to the primary creep and steady-state creep stages, respectively. The samples were compared with those before creep and after creep fracture. The microstructure of sample at different creep stages was analyzed by transmission electron microscopy. The submicrometer precipitated phases in persistent creep process was focused on. The results showed that the microstructures of P91 heat resistant steel were degraded in creep process, including the widening of martensite lath, the decrease of dislocation density and the slight coarsening of precipitated phase. Moreover, the new phases were formed. The precipitated phases of P91 steel mainly included the M23C6 phase (100-200 nm) and MX phase (10-50 nm). These two phases changed slightly in creep process. The Laves phase containing little Mo was observed when the creep time was 1 800 h. The size was in range of 50-150 nm. The Laves phase was mainly distributed on martensite lath boundary and subboundary, especially the position with several subgrains or lath junction. The composition of Laves phase was stable, but it was easily coarsened. The maximum Feret diameter in Laves phase in fracture sample after long-term creep (5 534 h) was higher than 600 nm. The fine Laves phase showed strong precipitation strengthening effect. However, the coarse Laves phase would weaken the strengthening effect. Moreover, the strength of matrix was reduced. As a result, the creep was accelerated, leading to the formation of crack even fracture.
��ǿ�� ���� ��ұ��. P91���ȸ�600 ���ʱ�����Ϊ̽��[J]. �й������ڿ���, 2015, 33(4): 1-5.
GAO Jia-qiang��WANG Qi-jiang��ZHOU Ye-dong. Discussion on the short-term creep behavior of P91 heat resistant steel at 600 ��. Chinese Journal of Iron and Steel, 2015, 33(4): 1-5.
2015, Vol. 33 
