690合金在高温水中的应力腐蚀裂纹扩展行为

CRACK GROWTH BEHAVIOR FOR STRESS CORROSION CRACKING OF 690 ALLOY IN HIGH TEMPERATURE WATER

用交流电位降(ACPD)技术实现了模拟压水堆一回路340℃高温水环境中690合金应力腐蚀裂纹扩展的实时监测.断口观察表明,2种一维冷加工690合金均出现沿晶应力腐蚀裂纹扩展,裂纹沿平行轧制方向的扩展速率略高于垂直轧制方向的速率;当溶解H浓度(C_(dH))由30μL/g减小到10μL/g时,经1075℃退火和700℃固溶处理15h并一维冷轧25%的T-L取向690合金的平均裂纹扩展速率由4.8×10^(-11)m/s增加至11.2×10^(-11)m/s;应力腐蚀裂纹扩展主要为内氧化机制.

Stress corrosion crack growth rates of alloy 690 thermally treated（TT） after one- directionally（1D） cold-rolling along the longitudinal（L） direction and three-directionally（3D） cold- rolling were successfully measured by ACPD technique in deoxygenated water with different dissolved hydrogen contents（C_（dH） at 340℃.The fracture mode is mainly intergranular mode in both two kinds of alloy 690TT.The crack growth rates in the T-L orientation are higher than those in the L-T orientation in 340℃deoxygenated environments.For 1D 25%alloy 690TT with T-L orientation, the measured average crack growth rate is 4.8×10^（-11） m/s in 340℃water with C_（dH） 30μL/g,and the measured average crack growth rate is l.l×l0^（-10） m/s in 340℃water with C_（dH） 10μL/g.The mechanism of crack growth is internal oxidation mechanism.