Effect of chromium content on stress corrosion cracking susceptibility of shielded metal arc weld metals for 600 type alloy in high-temperature pressurised pure water
Effect of chromium content on stress corrosion cracking susceptibility of shielded metal arc weld metals for 600 type alloy in high-temperature pressurised pure water
复制标题
铬含量对600型合金焊缝金属在高温加压纯水中应力腐蚀开裂敏感性的影响
DOI：
10.1080/09507116.2012.708499
复制
发表时间：
2013
影响因子：
--
通讯作者：
K. Ikeuchi
中科院分区：
文献类型：
--
作者：
S. Nishikawa;Y. Horii;K. Ikeuchi
本文研究了铬含量为14.8- 21.4mass %的Inconel 600合金在高温高压水介质中的应力腐蚀开裂（SCC）敏感性（对应沸水堆核电站的运行工况），因为含有18-22质量% Cr的合金82的TIG焊接金属比合金182的SMAW金属（Cr含量= 3-17质量%）具有更好的抗SCC性。当其Cr含量增加到与82合金相同的水平时，182合金的焊缝金属在焊态下仅维持轻微的SCC，并且在893 K的去应力退火和673 K的时效的焊后热处理去应力+低温时效（SR+LTA）后未检测到裂纹。这些结果表明，合金82的较高Cr含量是其比合金182更高的抗SCC性的原因。焊接过程中Cr碳化物在晶界处析出，SR+LTA处理也随Cr含量的增加由M7 C3型向M23 C6型转变。另外，进行了SR+LTA处理的Cr含量为14.8质量%的焊缝金属的晶界的Cr含量为3质量%，但Cr含量为18.5质量%的焊缝金属的Cr含量为10质量%以上。向合金182中添加Cr增加了晶界区域中的Cr含量，表明当晶界处的Cr含量不小于10质量%时，可以抑制晶间SCC。当施加SR+LTA处理时，在含有18.5质量% Cr的合金182中，除了碳化物之外，还在晶界处析出Ni 16（Mn，Cr）6Si 7（G相）。透射电子显微镜-EDS分析表明，G相富含P，因此可以降低晶界区域的P含量。可能是由于G相的析出降低了晶界P含量，从而提高了SR+LTA处理的182合金的抗SCC性能。
The stress corrosion cracking (SCC) susceptibility of SMAW metals for Inconel alloy 600 to which Cr was added to 14.8–21.4 mass% has been investigated on the basis of a creviced bent beam test in pressurized hot water (corresponding to the service condition of boiling water reactor nuclear power plant), since the TIG weld metal of alloy 82 involving 18–22 mass% Cr possesses much better resistance to SCC than the SMAW metal of alloy 182 (Cr content = 3–17 mass%). When their Cr contents were increased to the same level as those of the alloy 82, the weld metals of alloy 182 sustained only slight SCCs in the as-welded state, and no crack was detected after the post-weld heat treatment stress relief+low-temperature ageing (SR+LTA) of stress relief annealing at 893 K followed by ageing at 673 K. These results suggest that the higher Cr content of the alloy 82 is responsible for its higher resistance to SCC than that of the alloy 182. The Cr carbides precipitated at the grain boundary during the welding, and the SR+LTA treatment was also changed from M7C3 type to M23C6 type with the increase in the Cr content. Although the Cr content at the grain boundary in weld metal containing 14.8 mass% Cr subjected to the SR+LTA treatment was 3 mass%, the Cr content of weld metal containing 18.5 mass% Cr was not less than 10 mass%. The addition of the Cr to the alloy 182 increased the Cr content in the grain boundary region, suggesting that the inter-granular SCC can be suppressed when the Cr content at the grain boundary is not less than 10 mass%. In addition to the carbide, Ni16(Mn, Cr)6Si7 (G phase) was precipitated at the grain boundary in the alloy 182 containing 18.5 mass% Cr when the SR+LTA treatment was applied. transmission electron microscope-EDS analyses suggested that the G phase was enriched in P, and therefore could decrease the P content in the grain boundary region. Probably, the decreased P content at the grain boundary due to the precipitation of G phase contributed to the enhancement of the SCC resistance of the Cr-added alloy 182 by the SR+LTA treatment.