In this study, by performing visual inspection, chemical composition analysis, mechanical performance testing, micro-structure and micro-morphology analyses, a failure investigation is presented on the surfacing weld induced bursting of 20G water wall tube in a thermal power plant. Besides, to identify the environmental medium and deposits, the Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) have been conducted. The tube has undergone the localized wall thinning by fly-ash erosion burst after being repaired for 4000 h. As revealed from the macroscopic examination on the tube, significant corrosive products have been produced on the water-side of the surfacing layer position of the tube. According to the metallographic analysis of the rupture region, the massive widmanstatten overheated structure has been found in the heat-affected zone (HAZ). Furthermore, in the failure parent metal, extensive intergranular cracks, severe decarburization and mechanical performance degradation (∼20 HV₁₀) have been identified. The micro-morphology analysis has described the partial-melting process, spherical particles and the dendrite on the fracture surface. As revealed from the EDS and XRD results, the accumulation of Cu on the inner surface of the rupture region of the tube was demonstrated. The comprehensive study has suggested that the excessive welding heat-input leads to the generation of local over-heating and over-burning. Lastly, the electrochemical corrosion and the hydrogen corrosion cracking are generated in the inner wall of the welding region.

在这项研究中，通过进行目视检查，化学成分分析，力学性能测试，微观结构和微观形态分析，对火电厂20G水冷壁管堆焊引起的爆裂进行了故障研究。此外，为了识别环境介质和沉积物，还进行了能量色散光谱（EDS）和X射线衍射（XRD）。修复4000小时后，该管已因飞灰侵蚀而发生局部壁薄。如从对管子的宏观检查所揭示的那样，在管子的表面层位置的水侧已经产生了显着的腐蚀产物。根据断裂部位的金相分析，在热影响区（HAZ）中发现了大规模的widmanstatten过热结构。此外，在失效的母体金属中，广泛的晶间裂纹，严重的脱碳和机械性能下降（〜20 HV₁₀）已被识别。微观形貌分析描述了部分熔融过程，球形颗粒和断裂表面的枝晶。如从EDS和XRD结果所揭示的，证明了Cu在管的破裂区域的内表面上的累积。综合研究表明，过多的焊接热输入会导致局部过热和过度燃烧。最后，在焊接区域的内壁中产生电化学腐蚀和氢腐蚀裂纹。