利用P92钢在595、610、640、670℃的高应力试验条件下的蠕变试验数据,得出其Norton应力指数,依据Norton应力指数的大小判定其蠕变机理为位错蠕变.同时结合1种新的蠕变变形及断裂模型,引入将蠕变损伤看作1个内在的阶段变量的蠕变损伤容许量系数,根据蠕变损伤容许量λ=2.94,判断其蠕变变形和断裂是位错运动控制的.微观组织的观察也表明,蠕变后的试样中位错密度大大降低,高密度位错是P92钢持久强度高的原因,伴随着位错密度的下降,P92钢持久强度降低直至断裂.
The Norton stress exponents were calculated based on creep test with high stresses at 595, 610, 640, 670℃ of P92 steel. The creep mechanics was clarified as dislocation creep with the values of the Norton stress ex-ponents. And a new creep model which treated damage as an internal state variable named creep damage tolerance factor was analyzed as well. The creep and fracture mechanics was illustrated as dislocation controlled with the value of creep damage tolerance factor λ= 2.94. The microstructure investigation show that the dislocation density decreases dramatically after creep. The change show that high density dislocations are the reason of the excellent creep rupture strength of P92 steel. With decreasing dislocation density during creep, the creep rupture strength decreases and fractured finally.
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