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在650℃下对国产HR3C耐热钢进行了标准拉伸持久试验,采用外推法计算出该钢105h的持久强度极限达到104.98MPa。不同持久时间的样品硬度测试表明,随着持久时间增加,硬度上升,且晶界硬度高于晶内硬度。在持久时间2000 h左右达到峰值后开始缓慢下降,晶界和晶内硬度发生反转。断口观察显示,持久断裂的形态主要是沿晶断裂形态。利用SEM和EDS等对不同应力状态下的蠕变断裂试样微观组织进行了分析比较,随着持久时间的增加,耐热钢中析出相不断析出和长大,晶内析出细小弥散分布的NiCrN,起到显著的沉淀强化作用;晶界随持久时间延长明显宽化,准连续分布于晶界的主要碳化物M23C6长大速度快,明显降低晶界强度而弱化晶界表现出晶界脆化倾向,成为蠕变空洞形核地点。
The tensile test of the domestic HR3C heat-resistant steel was carried out at 650 ℃ for a long time, and the extension strength of the steel was calculated to reach 104.98MPa by extrapolation method. Sample hardness tests at different endurance times show that as the persistence time increases, the hardness increases and the grain boundary hardness is higher than the intragranular hardness. After reaching the peak value for about 2000 h, the hardness began to drop slowly, and the grain boundary and intracrystalline hardness reversed. Fracture observation shows that the shape of long-term fracture is mainly along the intergranular fracture morphology. The microstructures of creep rupture specimens under different stress states were analyzed and compared by SEM and EDS. With the increase of the lasting time, the precipitated phases in the heat-resisting steel continuously segregated and grew up, and fine and dispersed NiCrN . The grain boundary obviously widened with the prolongation of time. The growth of the main carbides M23C6, which are quasi-continuously distributed in the grain boundaries, grew rapidly, significantly reduced the grain boundary strength and weakened the grain boundaries and showed grain boundary embrittlement Tendency to become a cratered hollow nucleus site.