P92钢长期高温服役后组织性能试验分析

Experimental analysis on microstructure and properties of P92 steel after long-term service at high temperatures

采用化学成分分析、力学性能试验及微观组织分析等方法,分析了服役8.5万h的P92钢力学性能和微观组织,并与原始管分析结果进行对比。结果表明:P92钢经8.5万h高温服役后,除高温抗拉强度外,其他力学性能指标均满足标准对新管的要求;与原始管相比,服役管的性能已有明显劣化,室温规定塑性延伸强度下降了9.2%,室温抗拉强度下降了3.0%,室温断后伸长率下降了7.7%,室温纵向和横向冲击吸收能量分别下降了73%和65%,硬度下降了2.5%;与原始管在610 ℃相比,服役管在600 ℃的规定塑性延伸强度下降了6.1%;P92钢服役管的微观组织也有明显老化,虽然其金相组织中的马氏体组织形态仍明显,但亚结构中有局部马氏体板条发生回复,出现亚晶粒并等轴化,第二相在晶界和板条界析出较多,Laves相粗化明显。

The mechanical properties and microstructure of P92 steel after 85 000 hours’ service were analyzed by several test methods such as chemical composition analysis, mechanical property test and microstructure analysis,and the results were compared with that of the original tube. The results show that, after 85 000 hours’ service at high temperatures, all the P92 steel’s mechanical properties except high temperature tensile strength met the requirements of the standard for new pipes. Compared with the original pipe, the performance of the service pipe had been deteriorated obviously. The plastic elongation at room temperature decreased by 9.2%, the tensile strength at room temperature decreased by 3.0%, the elongation at room temperature after fracture decreased by7.7%, the longitudinal and transverse impact absorption energy at room temperature decreased by 73% and 65%,the hardness decreased by 2.5%, and the plastic elongation decreased by 6.1% at 600 ℃ compared with that of the original pipe at 610 ℃. Moreover, the microstructure of the service tube had obvious aging. Although the martensite morphology in the metallographic structure was still obvious, the local martensite lath in the substructure had the characteristics of recovery, sub-grain and equiaxed, the second phase precipitated greatly at grain boundary and lath boundary, and Laves phase coarsened obviously.