超超临界发电厂中P92钢蠕变特性及断裂机制

Creep properties and fracture mechanism of P92 steel used in ultra-supercritical power plant

P92钢因其在高温条件下具有优异的抗氧化性能、高温蠕变性能以及较低的热膨胀系数,而被广泛应用于超超临界发电厂的主蒸汽管道等厚壁部件。通过625、650℃不同应力条件下的高温蠕变试验以及运用金相显微镜(OM)、扫描电子显微镜(SEM)等微观分析技术对国产P92钢的蠕变特性及断裂机制进行了分析,并与国外生产的P92钢进行比较。结果表明:国产P92钢最小蠕变速率和蠕变破断寿命与蠕变应力之间的关系均遵循幂定律;国产P92钢的蠕变寿命明显低于国外P92钢,蠕变过程中Laves相的迅速长大和粗化是国产P92钢蠕变性能劣化的主要原因;Larson-Miller方法中,参数C=38时拟合的Larson-Miller曲线可以很好地与试验值吻合。

ASME P92 steel was widely used in ultra-supercritical power plant due to its excellent oxidation resistance,good combination of creep strength in high temperature and low thermal expansion coefficient. Creep experiments were conducted under different stress conditions at 625 ℃ and 650 ℃. Then,the creep characteristics and the fracture mechanism of domestic P92 steel were analyzed by a micro-analytic technique,such as optical microscope（ OM） and scanning electron microscope（ SEM）. Finally,results were compared between domestic and foreign P92 steels. The stress dependence of minimum creep rate and creep rupture life of domestic P92 obeyed power law. The creep life of domestic P92 steel was obviously lower than that of foreign steel,the fast growth and coarsening of Laves phase were the main reasons for domestic P92 steel premature creep rupture. Experimental data were fitted with Larson-Miller curves when C = 38.