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<p>The high-temperature superheater outlet pipe of a boiler failed after 70,000 hours of operation, which was below its expected service life. The failure mechanism was investigated through multiple tests, revealing that compound sulfate corrosion caused significant thinning of the pipe wall, with a maximum rate of 55%. The Brinell hardness decreased by 24HBW compared to the standard, and the tensile strength decreased by 75MPa compared to the standard. Corrosion analysis showed a multilayer structure: compound sulfate near the pipe wall, sulfate on the flue gas side, and a loose slag layer in the middle. Sulfur and oxygen, identified as the primary corrosive agents, penetrated the loose slag layer and caused continuous corrosion. This process led to local overheating, further accelerating degradation. Microstructural examination showed martensite transformed into ferrite after long-term operation, disrupting the material’s continuity and intensifying high-temperature creep. The combined effects of compound sulfate corrosion, creep, and microstructural changes ultimately resulted in pipe leakage. Based on the findings, preventive measures have been proposed to mitigate such failures and ensure the long-term reliability of similar equipment.</p>

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Failure Analysis of High-Temperature Superheater Outlet Pipes in Thermal Power Plants

  • 期刊论文

  • 发表日期：

    2025年6月27日

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  • Qiankun Li,
  • Song Xue,
  • Fengtao Hu,
  • Rongchao Li,
  • Ying Zhang,
  • Wenfu Yuan

摘要

The high-temperature superheater outlet pipe of a boiler failed after 70,000 hours of operation, which was below its expected service life. The failure mechanism was investigated through multiple tests, revealing that compound sulfate corrosion caused significant thinning of the pipe wall, with a maximum rate of 55%. The Brinell hardness decreased by 24HBW compared to the standard, and the tensile strength decreased by 75MPa compared to the standard. Corrosion analysis showed a multilayer structure: compound sulfate near the pipe wall, sulfate on the flue gas side, and a loose slag layer in the middle. Sulfur and oxygen, identified as the primary corrosive agents, penetrated the loose slag layer and caused continuous corrosion. This process led to local overheating, further accelerating degradation. Microstructural examination showed martensite transformed into ferrite after long-term operation, disrupting the material’s continuity and intensifying high-temperature creep. The combined effects of compound sulfate corrosion, creep, and microstructural changes ultimately resulted in pipe leakage. Based on the findings, preventive measures have been proposed to mitigate such failures and ensure the long-term reliability of similar equipment.