高温时效HR3C和T92耐热钢的老化行为及寿命预测

Aging behavior and life prediction of high-temperature aged HR3C and T92 heat resistant steels

HR3C及T92两种典型超(超)临界机组耐热钢分别在650~700℃进行高温时效,研究时效过程中显微组织结构和硬度的变化规律,建立硬度与Larson-Miller参数(P函数)间关系数学模型。结果表明,两种耐热钢的硬度均随时效温度升高显著降低;温度不变,随着时效时间的延长,HR3C耐热钢的硬度先增加后减小,而T92钢硬度单调下降,最后都趋于稳定。孪晶界消失以及晶界与晶内析出相的析出、长大是导致时效过程中两种耐热钢硬度变化的主要原因。采用线性拟合的方法,得到了时效耐热钢硬度与其P函数关系模型。基于相同P函数,计算所得时效钢硬度与测量的硬度吻合,该模型可用于服役耐热钢管服役寿命预测。

Artificial aging experiment of the HR3C and T92 steels,two typical heat resistant steels of the ultra-supercritical units,was carried out at 650 ℃ to 700 ℃ to investigate the microstructure evolution and hardness change of the steels during aging.Moreover,the relationship between the hardness of the each steel and the Larson-Miller parameter( P parameter) was modeled mathematically.The results show that the hardness values of the HR3C and the T92 steels decrease dramatically with the aging time.When the aging temperature is fixed,the hardness of HR3C increases and then decreases,and the hardness of T92 decreases monotonously,finally,the hardness values of HR3C and T92 turns to be constant,as the aging time extended.Disappearance of the twin grain boundaries,precipitation and growth of the second phases along the austenitic grain boundaries and in the austenitic grains are two main reasons of the change of the hardness values of the T92 and HR3C steels during the high-temperature aging.A mathematical model of the relationship between the hardness and the P parameter of T92 or HR3C is obtained via a linear fitting method.On the condition of the same P parameter,the calculated hardness values and the tested ones are coincided with each other very well.These mathematical models can be employed to predict the service life of those heat resistant steel tubes.