T91/TP347H异种钢焊接接头开裂失效分析

Failure analys is of cracking in T91/TP347H dissimilar steel weld joint

采用金相显微镜、背散射电子衍射系统、显微硬度计、万能材料实验机对350 MW超临界锅炉再热器发生开裂的T91/TP347异种钢焊接接头进行了检测和分析。结果表明,开裂由新型马氏体耐热钢Ⅳ型裂纹所致,开裂区域为异种钢接头T91钢热影响区的部分相变区。异种钢接头在服役过程中承受较高的应力,而部分相变区的微观组织导致其蠕变强度在接头中最低,高温服役过程中裂纹通过蠕变空洞连接方式在部分相变区形成并导致最终的开裂。

Optical micrography,electron back scattered diffraction system,microhardness tester and universal material testing machine were used to detect and analyze the cracked T91/TP347H dissimilar steel weld joint of the reheater in a 350 MW supercritical boiler.Results show that,the crack was caused by typeⅣcracking of new type martensite heat resistant steel and the cracking region located in the intercritical HAZ of the T91 side in the dissimilar steel weld joint.The dissimilar steel weld joint withstood relatively higher stress during the service process,while the intercritical HAZ possesses the lowest creep strength due to its microstructure feature.Crack was formed by the mode of creep void interconnection in the intercritical HAZ during the high temperature service process and led to the final cracking.